refactor(docs-infra): fix docs examples for tslint rule prefer-const (#38143)

This commit updates the docs examples to be compatible with the
`prefer-const` tslint rule.

This is in preparation of updating the docs examples `tslint.json` to
match the one generated for new Angular CLI apps in a future commit.

PR Close #38143

aio/content/examples/ajs-quick-reference/e2e/src/app.e2e-spec.ts

@@ -12,7 +12,7 @@ describe('AngularJS to Angular Quick Reference Tests', () => {
 
   it('should display proper movie data', () => {
     // We check only a few samples
-    let expectedSamples: any[] = [
+    const expectedSamples: any[] = [
       {row: 0, column: 0, element: 'img', attr: 'src', value: 'images/hero.png', contains: true},
       {row: 0, column: 2, value: 'Celeritas'},
       {row: 1, column: 3, matches: /Dec 1[678], 2015/}, // absorb timezone dif; we care about date format
@@ -23,18 +23,18 @@ describe('AngularJS to Angular Quick Reference Tests', () => {
     ];
 
     // Go through the samples
-    let movieRows = getMovieRows();
+    const movieRows = getMovieRows();
     for (let i = 0; i < expectedSamples.length; i++) {
-      let sample = expectedSamples[i];
+      const sample = expectedSamples[i];
-      let tableCell = movieRows.get(sample.row)
+      const tableCell = movieRows.get(sample.row)
         .all(by.tagName('td')).get(sample.column);
       // Check the cell or its nested element
-      let elementToCheck = sample.element
+      const elementToCheck = sample.element
         ? tableCell.element(by.tagName(sample.element))
         : tableCell;
 
       // Check element attribute or text
-      let valueToCheck = sample.attr
+      const valueToCheck = sample.attr
         ? elementToCheck.getAttribute(sample.attr)
         : elementToCheck.getText();
 
@@ -70,18 +70,18 @@ describe('AngularJS to Angular Quick Reference Tests', () => {
   });
 
   function testImagesAreDisplayed(isDisplayed: boolean) {
-    let expectedMovieCount = 3;
+    const expectedMovieCount = 3;
 
-    let movieRows = getMovieRows();
+    const movieRows = getMovieRows();
     expect(movieRows.count()).toBe(expectedMovieCount);
     for (let i = 0; i < expectedMovieCount; i++) {
-      let movieImage = movieRows.get(i).element(by.css('td > img'));
+      const movieImage = movieRows.get(i).element(by.css('td > img'));
       expect(movieImage.isDisplayed()).toBe(isDisplayed);
     }
   }
 
   function testPosterButtonClick(expectedButtonText: string, isDisplayed: boolean) {
-    let posterButton = element(by.css('app-movie-list tr > th > button'));
+    const posterButton = element(by.css('app-movie-list tr > th > button'));
     expect(posterButton.getText()).toBe(expectedButtonText);
 
     posterButton.click().then(() => {
@@ -94,10 +94,10 @@ describe('AngularJS to Angular Quick Reference Tests', () => {
   }
 
   function testFavoriteHero(heroName: string, expectedLabel: string) {
-    let movieListComp = element(by.tagName('app-movie-list'));
+    const movieListComp = element(by.tagName('app-movie-list'));
-    let heroInput = movieListComp.element(by.tagName('input'));
+    const heroInput = movieListComp.element(by.tagName('input'));
-    let favoriteHeroLabel = movieListComp.element(by.tagName('h3'));
+    const favoriteHeroLabel = movieListComp.element(by.tagName('h3'));
-    let resultLabel = movieListComp.element(by.css('span > p'));
+    const resultLabel = movieListComp.element(by.css('span > p'));
 
     heroInput.clear().then(() => {
       heroInput.sendKeys(heroName || '');

aio/content/examples/architecture/e2e/src/app.e2e-spec.ts

@@ -19,7 +19,7 @@ describe('Architecture', () => {
   });
 
   it(`has h2 '${expectedH2}'`, () => {
-    let h2 = element.all(by.css('h2')).map((elt: any) => elt.getText());
+    const h2 = element.all(by.css('h2')).map((elt: any) => elt.getText());
     expect(h2).toEqual(expectedH2);
   });
 
@@ -32,29 +32,29 @@ function heroTests() {
   const targetHero: Hero = { id: 2, name: 'Dr Nice' };
 
   it('has the right number of heroes', () => {
-    let page = getPageElts();
+    const page = getPageElts();
     expect(page.heroes.count()).toEqual(3);
   });
 
   it('has no hero details initially', () => {
-    let page = getPageElts();
+    const page = getPageElts();
     expect(page.heroDetail.isPresent()).toBeFalsy('no hero detail');
   });
 
   it('shows selected hero details', async () => {
     await element(by.cssContainingText('li', targetHero.name)).click();
-    let page = getPageElts();
+    const page = getPageElts();
-    let hero = await heroFromDetail(page.heroDetail);
+    const hero = await heroFromDetail(page.heroDetail);
     expect(hero.id).toEqual(targetHero.id);
     expect(hero.name).toEqual(targetHero.name);
   });
 
   it(`shows updated hero name in details`, async () => {
-    let input = element.all(by.css('input')).first();
+    const input = element.all(by.css('input')).first();
     input.sendKeys(nameSuffix);
-    let page = getPageElts();
+    const page = getPageElts();
-    let hero = await heroFromDetail(page.heroDetail);
+    const hero = await heroFromDetail(page.heroDetail);
-    let newName = targetHero.name + nameSuffix;
+    const newName = targetHero.name + nameSuffix;
     expect(hero.id).toEqual(targetHero.id);
     expect(hero.name).toEqual(newName);
   });
@@ -62,12 +62,12 @@ function heroTests() {
 
 function salesTaxTests() {
   it('has no sales tax initially', () => {
-    let page = getPageElts();
+    const page = getPageElts();
     expect(page.salesTaxDetail.isPresent()).toBeFalsy('no sales tax info');
   });
 
   it('shows sales tax', async () => {
-    let page = getPageElts();
+    const page = getPageElts();
     page.salesTaxAmountInput.sendKeys('10', protractor.Key.ENTER);
     expect(page.salesTaxDetail.getText()).toEqual('The sales tax is $1.00');
   });
@@ -86,9 +86,9 @@ function getPageElts() {
 
 async function heroFromDetail(detail: ElementFinder): Promise<Hero> {
   // Get hero id from the first <div>
-  let id = await detail.all(by.css('div')).first().getText();
+  const id = await detail.all(by.css('div')).first().getText();
   // Get name from the h2
-  let name = await detail.element(by.css('h4')).getText();
+  const name = await detail.element(by.css('h4')).getText();
   return {
     id: +id.substr(id.indexOf(' ') + 1),
     name: name.substr(0, name.lastIndexOf(' ')),

aio/content/examples/architecture/src/app/backend.service.ts

@@ -18,7 +18,7 @@ export class BackendService {
       // TODO: get from the database
       return Promise.resolve<Hero[]>(HEROES);
     }
-    let err = new Error('Cannot get object of this type');
+    const err = new Error('Cannot get object of this type');
     this.logger.error(err);
     throw err;
   }

aio/content/examples/architecture/src/app/sales-tax.service.ts

@@ -7,7 +7,7 @@ export class SalesTaxService {
   constructor(private rateService: TaxRateService) { }
 
   getVAT(value: string | number) {
-    let amount = (typeof value === 'string') ?
+    const amount = (typeof value === 'string') ?
       parseFloat(value) : value;
     return (amount || 0) * this.rateService.getRate('VAT');
   }

aio/content/examples/attribute-directives/e2e/src/app.e2e-spec.ts

@@ -2,7 +2,7 @@ import { browser, element, by } from 'protractor';
 
 describe('Attribute directives', () => {
 
-  let title = 'My First Attribute Directive';
+  const title = 'My First Attribute Directive';
 
   beforeAll(() => {
     browser.get('');

aio/content/examples/binding-syntax/e2e/src/app.e2e-spec.ts

@@ -36,22 +36,22 @@ describe('Binding syntax e2e tests', () => {
 
 
   it('should log a message including Sarah', async () => {
-    let attributeButton = element.all(by.css('button')).get(1);
+    const attributeButton = element.all(by.css('button')).get(1);
     await attributeButton.click();
     const contents = 'Sarah';
     logChecker(attributeButton, contents);
   });
 
   it('should log a message including Sarah for DOM property', async () => {
-    let DOMPropertyButton = element.all(by.css('button')).get(2);
+    const DOMPropertyButton = element.all(by.css('button')).get(2);
     await DOMPropertyButton.click();
     const contents = 'Sarah';
     logChecker(DOMPropertyButton, contents);
   });
 
   it('should log a message including Sally for DOM property', async () => {
-    let DOMPropertyButton = element.all(by.css('button')).get(2);
+    const DOMPropertyButton = element.all(by.css('button')).get(2);
-    let input = element(by.css('input'));
+    const input = element(by.css('input'));
     input.sendKeys('Sally');
     await DOMPropertyButton.click();
     const contents = 'Sally';
@@ -59,14 +59,14 @@ describe('Binding syntax e2e tests', () => {
   });
 
   it('should log a message that Test Button works', async () => {
-    let testButton = element.all(by.css('button')).get(3);
+    const testButton = element.all(by.css('button')).get(3);
     await testButton.click();
     const contents = 'Test';
     logChecker(testButton, contents);
   });
 
   it('should toggle Test Button disabled', async () => {
-    let toggleButton = element.all(by.css('button')).get(4);
+    const toggleButton = element.all(by.css('button')).get(4);
     await toggleButton.click();
     const contents = 'true';
     logChecker(toggleButton, contents);

aio/content/examples/binding-syntax/src/app/app.component.ts

@@ -26,7 +26,7 @@ export class AppComponent {
 
   toggleDisabled(): any {
 
-    let testButton = document.getElementById('testButton') as HTMLInputElement;
+    const testButton = document.getElementById('testButton') as HTMLInputElement;
     testButton.disabled = !testButton.disabled;
     console.warn(testButton.disabled);
   }

aio/content/examples/built-in-directives/e2e/src/app.e2e-spec.ts

@@ -7,13 +7,13 @@ describe('Built-in Directives', () => {
   });
 
   it('should have title Built-in Directives', () => {
-    let title = element.all(by.css('h1')).get(0);
+    const title = element.all(by.css('h1')).get(0);
     expect(title.getText()).toEqual('Built-in Directives');
   });
 
   it('should change first Teapot header', async () => {
-    let firstLabel = element.all(by.css('p')).get(0);
+    const firstLabel = element.all(by.css('p')).get(0);
-    let firstInput = element.all(by.css('input')).get(0);
+    const firstInput = element.all(by.css('input')).get(0);
 
     expect(firstLabel.getText()).toEqual('Current item name: Teapot');
     firstInput.sendKeys('abc');
@@ -22,48 +22,48 @@ describe('Built-in Directives', () => {
 
 
   it('should modify sentence when modified checkbox checked', () => {
-    let modifiedChkbxLabel = element.all(by.css('input[type="checkbox"]')).get(1);
+    const modifiedChkbxLabel = element.all(by.css('input[type="checkbox"]')).get(1);
-    let modifiedSentence = element.all(by.css('div')).get(1);
+    const modifiedSentence = element.all(by.css('div')).get(1);
 
     modifiedChkbxLabel.click();
     expect(modifiedSentence.getText()).toContain('modified');
   });
 
   it('should modify sentence when normal checkbox checked', () => {
-    let normalChkbxLabel = element.all(by.css('input[type="checkbox"]')).get(4);
+    const normalChkbxLabel = element.all(by.css('input[type="checkbox"]')).get(4);
-    let normalSentence = element.all(by.css('div')).get(7);
+    const normalSentence = element.all(by.css('div')).get(7);
 
     normalChkbxLabel.click();
     expect(normalSentence.getText()).toContain('normal weight and, extra large');
   });
 
   it('should toggle app-item-detail', () => {
-    let toggleButton = element.all(by.css('button')).get(3);
+    const toggleButton = element.all(by.css('button')).get(3);
-    let toggledDiv = element.all(by.css('app-item-detail')).get(0);
+    const toggledDiv = element.all(by.css('app-item-detail')).get(0);
 
     toggleButton.click();
     expect(toggledDiv.isDisplayed()).toBe(true);
   });
 
   it('should hide app-item-detail', () => {
-    let hiddenMessage = element.all(by.css('p')).get(11);
+    const hiddenMessage = element.all(by.css('p')).get(11);
-    let hiddenDiv = element.all(by.css('app-item-detail')).get(2);
+    const hiddenDiv = element.all(by.css('app-item-detail')).get(2);
 
     expect(hiddenMessage.getText()).toContain('in the DOM');
     expect(hiddenDiv.isDisplayed()).toBe(true);
   });
 
   it('should have 10 lists each containing the string Teapot', () => {
-    let listDiv = element.all(by.cssContainingText('.box', 'Teapot'));
+    const listDiv = element.all(by.cssContainingText('.box', 'Teapot'));
     expect(listDiv.count()).toBe(10);
   });
 
   it('should switch case', () => {
-    let tvRadioButton = element.all(by.css('input[type="radio"]')).get(3);
+    const tvRadioButton = element.all(by.css('input[type="radio"]')).get(3);
-    let tvDiv = element(by.css('app-lost-item'));
+    const tvDiv = element(by.css('app-lost-item'));
 
-    let fishbowlRadioButton = element.all(by.css('input[type="radio"]')).get(4);
+    const fishbowlRadioButton = element.all(by.css('input[type="radio"]')).get(4);
-    let fishbowlDiv = element(by.css('app-unknown-item'));
+    const fishbowlDiv = element(by.css('app-unknown-item'));
 
     tvRadioButton.click();
     expect(tvDiv.getText()).toContain('Television');

aio/content/examples/built-in-template-functions/e2e/src/app.e2e-spec.ts

@@ -6,12 +6,12 @@ describe('Built Template Functions Example', () => {
   });
 
   it('should have title Built-in Template Functions', () => {
-    let title = element.all(by.css('h1')).get(0);
+    const title = element.all(by.css('h1')).get(0);
     expect(title.getText()).toEqual('Built-in Template Functions');
   });
 
   it('should display $any( ) in h2', () => {
-    let header = element(by.css('h2'));
+    const header = element(by.css('h2'));
     expect(header.getText()).toContain('$any( )');
   });
 

aio/content/examples/component-interaction/e2e/src/app.e2e-spec.ts

@@ -11,16 +11,16 @@ describe('Component Communication Cookbook Tests', () => {
   describe('Parent-to-child communication', () => {
     // #docregion parent-to-child
     // ...
-    let heroNames = ['Dr IQ', 'Magneta', 'Bombasto'];
+    const heroNames = ['Dr IQ', 'Magneta', 'Bombasto'];
-    let masterName = 'Master';
+    const masterName = 'Master';
 
     it('should pass properties to children properly', () => {
-      let parent = element.all(by.tagName('app-hero-parent')).get(0);
+      const parent = element.all(by.tagName('app-hero-parent')).get(0);
-      let heroes = parent.all(by.tagName('app-hero-child'));
+      const heroes = parent.all(by.tagName('app-hero-child'));
 
       for (let i = 0; i < heroNames.length; i++) {
-        let childTitle = heroes.get(i).element(by.tagName('h3')).getText();
+        const childTitle = heroes.get(i).element(by.tagName('h3')).getText();
-        let childDetail = heroes.get(i).element(by.tagName('p')).getText();
+        const childDetail = heroes.get(i).element(by.tagName('p')).getText();
         expect(childTitle).toEqual(heroNames[i] + ' says:');
         expect(childDetail).toContain(masterName);
       }
@@ -33,22 +33,22 @@ describe('Component Communication Cookbook Tests', () => {
     // #docregion parent-to-child-setter
     // ...
     it('should display trimmed, non-empty names', () => {
-      let nonEmptyNameIndex = 0;
+      const nonEmptyNameIndex = 0;
-      let nonEmptyName = '"Dr IQ"';
+      const nonEmptyName = '"Dr IQ"';
-      let parent = element.all(by.tagName('app-name-parent')).get(0);
+      const parent = element.all(by.tagName('app-name-parent')).get(0);
-      let hero = parent.all(by.tagName('app-name-child')).get(nonEmptyNameIndex);
+      const hero = parent.all(by.tagName('app-name-child')).get(nonEmptyNameIndex);
 
-      let displayName = hero.element(by.tagName('h3')).getText();
+      const displayName = hero.element(by.tagName('h3')).getText();
       expect(displayName).toEqual(nonEmptyName);
     });
 
     it('should replace empty name with default name', () => {
-      let emptyNameIndex = 1;
+      const emptyNameIndex = 1;
-      let defaultName = '"<no name set>"';
+      const defaultName = '"<no name set>"';
-      let parent = element.all(by.tagName('app-name-parent')).get(0);
+      const parent = element.all(by.tagName('app-name-parent')).get(0);
-      let hero = parent.all(by.tagName('app-name-child')).get(emptyNameIndex);
+      const hero = parent.all(by.tagName('app-name-child')).get(emptyNameIndex);
 
-      let displayName = hero.element(by.tagName('h3')).getText();
+      const displayName = hero.element(by.tagName('h3')).getText();
       expect(displayName).toEqual(defaultName);
     });
     // ...
@@ -60,10 +60,10 @@ describe('Component Communication Cookbook Tests', () => {
     // ...
     // Test must all execute in this exact order
     it('should set expected initial values', () => {
-      let actual = getActual();
+      const actual = getActual();
 
-      let initialLabel = 'Version 1.23';
+      const initialLabel = 'Version 1.23';
-      let initialLog = 'Initial value of major set to 1, Initial value of minor set to 23';
+      const initialLog = 'Initial value of major set to 1, Initial value of minor set to 23';
 
       expect(actual.label).toBe(initialLabel);
       expect(actual.count).toBe(1);
@@ -71,15 +71,15 @@ describe('Component Communication Cookbook Tests', () => {
     });
 
     it('should set expected values after clicking \'Minor\' twice', () => {
-      let repoTag = element(by.tagName('app-version-parent'));
+      const repoTag = element(by.tagName('app-version-parent'));
-      let newMinorButton = repoTag.all(by.tagName('button')).get(0);
+      const newMinorButton = repoTag.all(by.tagName('button')).get(0);
 
       newMinorButton.click().then(() => {
         newMinorButton.click().then(() => {
-          let actual = getActual();
+          const actual = getActual();
 
-          let labelAfter2Minor = 'Version 1.25';
+          const labelAfter2Minor = 'Version 1.25';
-          let logAfter2Minor = 'minor changed from 24 to 25';
+          const logAfter2Minor = 'minor changed from 24 to 25';
 
           expect(actual.label).toBe(labelAfter2Minor);
           expect(actual.count).toBe(3);
@@ -89,14 +89,14 @@ describe('Component Communication Cookbook Tests', () => {
     });
 
     it('should set expected values after clicking \'Major\' once', () => {
-      let repoTag = element(by.tagName('app-version-parent'));
+      const repoTag = element(by.tagName('app-version-parent'));
-      let newMajorButton = repoTag.all(by.tagName('button')).get(1);
+      const newMajorButton = repoTag.all(by.tagName('button')).get(1);
 
       newMajorButton.click().then(() => {
-        let actual = getActual();
+        const actual = getActual();
 
-        let labelAfterMajor = 'Version 2.0';
+        const labelAfterMajor = 'Version 2.0';
-        let logAfterMajor = 'major changed from 1 to 2, minor changed from 25 to 0';
+        const logAfterMajor = 'major changed from 1 to 2, minor changed from 25 to 0';
 
         expect(actual.label).toBe(labelAfterMajor);
         expect(actual.count).toBe(4);
@@ -105,10 +105,10 @@ describe('Component Communication Cookbook Tests', () => {
     });
 
     function getActual() {
-      let versionTag = element(by.tagName('app-version-child'));
+      const versionTag = element(by.tagName('app-version-child'));
-      let label = versionTag.element(by.tagName('h3')).getText();
+      const label = versionTag.element(by.tagName('h3')).getText();
-      let ul = versionTag.element((by.tagName('ul')));
+      const ul = versionTag.element((by.tagName('ul')));
-      let logs = ul.all(by.tagName('li'));
+      const logs = ul.all(by.tagName('li'));
 
       return {
         label,
@@ -125,26 +125,26 @@ describe('Component Communication Cookbook Tests', () => {
     // #docregion child-to-parent
     // ...
     it('should not emit the event initially', () => {
-      let voteLabel = element(by.tagName('app-vote-taker'))
+      const voteLabel = element(by.tagName('app-vote-taker'))
         .element(by.tagName('h3')).getText();
       expect(voteLabel).toBe('Agree: 0, Disagree: 0');
     });
 
     it('should process Agree vote', () => {
-      let agreeButton1 = element.all(by.tagName('app-voter')).get(0)
+      const agreeButton1 = element.all(by.tagName('app-voter')).get(0)
         .all(by.tagName('button')).get(0);
       agreeButton1.click().then(() => {
-        let voteLabel = element(by.tagName('app-vote-taker'))
+        const voteLabel = element(by.tagName('app-vote-taker'))
           .element(by.tagName('h3')).getText();
         expect(voteLabel).toBe('Agree: 1, Disagree: 0');
       });
     });
 
     it('should process Disagree vote', () => {
-      let agreeButton1 = element.all(by.tagName('app-voter')).get(1)
+      const agreeButton1 = element.all(by.tagName('app-voter')).get(1)
         .all(by.tagName('button')).get(1);
       agreeButton1.click().then(() => {
-        let voteLabel = element(by.tagName('app-vote-taker'))
+        const voteLabel = element(by.tagName('app-vote-taker'))
           .element(by.tagName('h3')).getText();
         expect(voteLabel).toBe('Agree: 1, Disagree: 1');
       });
@@ -167,19 +167,19 @@ describe('Component Communication Cookbook Tests', () => {
     // #docregion countdown-timer-tests
     // ...
     it('timer and parent seconds should match', () => {
-      let parent = element(by.tagName(parentTag));
+      const parent = element(by.tagName(parentTag));
-      let message = parent.element(by.tagName('app-countdown-timer')).getText();
+      const message = parent.element(by.tagName('app-countdown-timer')).getText();
       browser.sleep(10); // give `seconds` a chance to catchup with `message`
-      let seconds = parent.element(by.className('seconds')).getText();
+      const seconds = parent.element(by.className('seconds')).getText();
       expect(message).toContain(seconds);
     });
 
     it('should stop the countdown', () => {
-      let parent = element(by.tagName(parentTag));
+      const parent = element(by.tagName(parentTag));
-      let stopButton = parent.all(by.tagName('button')).get(1);
+      const stopButton = parent.all(by.tagName('button')).get(1);
 
       stopButton.click().then(() => {
-        let message = parent.element(by.tagName('app-countdown-timer')).getText();
+        const message = parent.element(by.tagName('app-countdown-timer')).getText();
         expect(message).toContain('Holding');
       });
     });
@@ -192,10 +192,10 @@ describe('Component Communication Cookbook Tests', () => {
     // #docregion bidirectional-service
     // ...
     it('should announce a mission', () => {
-      let missionControl = element(by.tagName('app-mission-control'));
+      const missionControl = element(by.tagName('app-mission-control'));
-      let announceButton = missionControl.all(by.tagName('button')).get(0);
+      const announceButton = missionControl.all(by.tagName('button')).get(0);
       announceButton.click().then(() => {
-        let history = missionControl.all(by.tagName('li'));
+        const history = missionControl.all(by.tagName('li'));
         expect(history.count()).toBe(1);
         expect(history.get(0).getText()).toMatch(/Mission.* announced/);
       });
@@ -214,11 +214,11 @@ describe('Component Communication Cookbook Tests', () => {
     });
 
     function testConfirmMission(buttonIndex: number, expectedLogCount: number, astronaut: string) {
-      let confirmedLog = ' confirmed the mission';
+      const confirmedLog = ' confirmed the mission';
-      let missionControl = element(by.tagName('app-mission-control'));
+      const missionControl = element(by.tagName('app-mission-control'));
-      let confirmButton = missionControl.all(by.tagName('button')).get(buttonIndex);
+      const confirmButton = missionControl.all(by.tagName('button')).get(buttonIndex);
       confirmButton.click().then(() => {
-        let history = missionControl.all(by.tagName('li'));
+        const history = missionControl.all(by.tagName('li'));
         expect(history.count()).toBe(expectedLogCount);
         expect(history.get(expectedLogCount - 1).getText()).toBe(astronaut + confirmedLog);
       });

aio/content/examples/component-interaction/src/app/app.module.ts

@@ -15,7 +15,7 @@ import { VersionParentComponent } from './version-parent.component';
 import { VoterComponent } from './voter.component';
 import { VoteTakerComponent } from './votetaker.component';
 
-let directives: any[] = [
+const directives: any[] = [
     AppComponent,
     AstronautComponent,
     CountdownTimerComponent,
@@ -30,7 +30,7 @@ let directives: any[] = [
     VoteTakerComponent
   ];
 
-let schemas: any[] = [];
+const schemas: any[] = [];
 
 // Include Countdown examples
 // unless in e2e tests which they break.

aio/content/examples/component-interaction/src/app/missioncontrol.component.ts

@@ -34,7 +34,7 @@ export class MissionControlComponent {
   }
 
   announce() {
-    let mission = this.missions[this.nextMission++];
+    const mission = this.missions[this.nextMission++];
     this.missionService.announceMission(mission);
     this.history.push(`Mission "${mission}" announced`);
     if (this.nextMission >= this.missions.length) { this.nextMission = 0; }

aio/content/examples/component-interaction/src/app/version-child.component.ts

@@ -18,14 +18,14 @@ export class VersionChildComponent implements OnChanges {
   changeLog: string[] = [];
 
   ngOnChanges(changes: {[propKey: string]: SimpleChange}) {
-    let log: string[] = [];
+    const log: string[] = [];
-    for (let propName in changes) {
+    for (const propName in changes) {
-      let changedProp = changes[propName];
+      const changedProp = changes[propName];
-      let to = JSON.stringify(changedProp.currentValue);
+      const to = JSON.stringify(changedProp.currentValue);
       if (changedProp.isFirstChange()) {
         log.push(`Initial value of ${propName} set to ${to}`);
       } else {
-        let from = JSON.stringify(changedProp.previousValue);
+        const from = JSON.stringify(changedProp.previousValue);
         log.push(`${propName} changed from ${from} to ${to}`);
       }
     }

aio/content/examples/component-styles/e2e/src/app.e2e-spec.ts

@@ -7,8 +7,8 @@ describe('Component Style Tests', () => {
   });
 
   it('scopes component styles to component view', () => {
-    let componentH1 = element(by.css('app-root > h1'));
+    const componentH1 = element(by.css('app-root > h1'));
-    let externalH1 = element(by.css('body > h1'));
+    const externalH1 = element(by.css('body > h1'));
 
     // Note: sometimes webdriver returns the fontWeight as "normal",
     // other times as "400", both of which are equal in CSS terms.
@@ -18,48 +18,48 @@ describe('Component Style Tests', () => {
 
 
   it('allows styling :host element', () => {
-    let host = element(by.css('app-hero-details'));
+    const host = element(by.css('app-hero-details'));
 
     expect(host.getCssValue('borderWidth')).toEqual('1px');
   });
 
   it('supports :host() in function form', () => {
-    let host = element(by.css('app-hero-details'));
+    const host = element(by.css('app-hero-details'));
 
     host.element(by.buttonText('Activate')).click();
     expect(host.getCssValue('borderWidth')).toEqual('3px');
   });
 
   it('allows conditional :host-context() styling', () => {
-    let h2 = element(by.css('app-hero-details h2'));
+    const h2 = element(by.css('app-hero-details h2'));
 
     expect(h2.getCssValue('backgroundColor')).toEqual('rgba(238, 238, 255, 1)'); // #eeeeff
   });
 
   it('styles both view and content children with /deep/', () => {
-    let viewH3 = element(by.css('app-hero-team h3'));
+    const viewH3 = element(by.css('app-hero-team h3'));
-    let contentH3 = element(by.css('app-hero-controls h3'));
+    const contentH3 = element(by.css('app-hero-controls h3'));
 
     expect(viewH3.getCssValue('fontStyle')).toEqual('italic');
     expect(contentH3.getCssValue('fontStyle')).toEqual('italic');
   });
 
   it('includes styles loaded with CSS @import', () => {
-    let host = element(by.css('app-hero-details'));
+    const host = element(by.css('app-hero-details'));
 
     expect(host.getCssValue('padding')).toEqual('10px');
   });
 
   it('processes template inline styles', () => {
-    let button = element(by.css('app-hero-controls button'));
+    const button = element(by.css('app-hero-controls button'));
-    let externalButton = element(by.css('body > button'));
+    const externalButton = element(by.css('body > button'));
     expect(button.getCssValue('backgroundColor')).toEqual('rgba(255, 255, 255, 1)'); // #ffffff
     expect(externalButton.getCssValue('backgroundColor')).not.toEqual('rgba(255, 255, 255, 1)');
   });
 
   it('processes template <link>s', () => {
-    let li = element(by.css('app-hero-team li:first-child'));
+    const li = element(by.css('app-hero-team li:first-child'));
-    let externalLi = element(by.css('body > ul li'));
+    const externalLi = element(by.css('body > ul li'));
 
     expect(li.getCssValue('listStyleType')).toEqual('square');
     expect(externalLi.getCssValue('listStyleType')).not.toEqual('square');

aio/content/examples/dependency-injection-in-action/e2e/src/app.e2e-spec.ts

@@ -7,68 +7,68 @@ describe('Dependency Injection Cookbook', () => {
     });
 
     it('should render Logged in User example', () => {
-      let loggedInUser = element.all(by.xpath('//h3[text()="Logged in user"]')).get(0);
+      const loggedInUser = element.all(by.xpath('//h3[text()="Logged in user"]')).get(0);
       expect(loggedInUser).toBeDefined();
     });
 
     it('"Bombasto" should be the logged in user', () => {
-      let loggedInUser = element.all(by.xpath('//div[text()="Name: Bombasto"]')).get(0);
+      const loggedInUser = element.all(by.xpath('//div[text()="Name: Bombasto"]')).get(0);
       expect(loggedInUser).toBeDefined();
     });
 
     it('should render sorted heroes', () => {
-      let sortedHeroes = element.all(by.xpath('//h3[text()="Sorted Heroes" and position()=1]')).get(0);
+      const sortedHeroes = element.all(by.xpath('//h3[text()="Sorted Heroes" and position()=1]')).get(0);
       expect(sortedHeroes).toBeDefined();
     });
 
     it('Dr Nice should be in sorted heroes', () => {
-      let sortedHero = element.all(by.xpath('//sorted-heroes/[text()="Dr Nice" and position()=2]')).get(0);
+      const sortedHero = element.all(by.xpath('//sorted-heroes/[text()="Dr Nice" and position()=2]')).get(0);
       expect(sortedHero).toBeDefined();
     });
 
     it('RubberMan should be in sorted heroes', () => {
-      let sortedHero = element.all(by.xpath('//sorted-heroes/[text()="RubberMan" and position()=3]')).get(0);
+      const sortedHero = element.all(by.xpath('//sorted-heroes/[text()="RubberMan" and position()=3]')).get(0);
       expect(sortedHero).toBeDefined();
     });
 
     it('Magma should be in sorted heroes', () => {
-      let sortedHero = element.all(by.xpath('//sorted-heroes/[text()="Magma"]')).get(0);
+      const sortedHero = element.all(by.xpath('//sorted-heroes/[text()="Magma"]')).get(0);
       expect(sortedHero).toBeDefined();
     });
 
     it('should render Hero of the Month', () => {
-      let heroOfTheMonth = element.all(by.xpath('//h3[text()="Hero of the month"]')).get(0);
+      const heroOfTheMonth = element.all(by.xpath('//h3[text()="Hero of the month"]')).get(0);
       expect(heroOfTheMonth).toBeDefined();
     });
 
     it('should render Hero Bios', () => {
-      let heroBios = element.all(by.xpath('//h3[text()="Hero Bios"]')).get(0);
+      const heroBios = element.all(by.xpath('//h3[text()="Hero Bios"]')).get(0);
       expect(heroBios).toBeDefined();
     });
 
     it('should render Magma\'s description in Hero Bios', () => {
-      let magmaText =  element.all(by.xpath('//textarea[text()="Hero of all trades"]')).get(0);
+      const magmaText =  element.all(by.xpath('//textarea[text()="Hero of all trades"]')).get(0);
       expect(magmaText).toBeDefined();
     });
 
     it('should render Magma\'s phone in Hero Bios and Contacts', () => {
-      let magmaPhone =  element.all(by.xpath('//div[text()="Phone #: 555-555-5555"]')).get(0);
+      const magmaPhone =  element.all(by.xpath('//div[text()="Phone #: 555-555-5555"]')).get(0);
       expect(magmaPhone).toBeDefined();
     });
 
     it('should render Hero-of-the-Month runner-ups', () => {
-      let runnersUp =  element(by.id('rups1')).getText();
+      const runnersUp =  element(by.id('rups1')).getText();
       expect(runnersUp).toContain('RubberMan, Dr Nice');
     });
 
     it('should render DateLogger log entry in Hero-of-the-Month', () => {
-      let logs =  element.all(by.id('logs')).get(0).getText();
+      const logs =  element.all(by.id('logs')).get(0).getText();
       expect(logs).toContain('INFO: starting up at');
     });
 
     it('should highlight Hero Bios and Contacts container when mouseover', () => {
-      let target = element(by.css('div[appHighlight="yellow"]'));
+      const target = element(by.css('div[appHighlight="yellow"]'));
-      let yellow = 'rgba(255, 255, 0, 1)';
+      const yellow = 'rgba(255, 255, 0, 1)';
 
       expect(target.getCssValue('background-color')).not.toEqual(yellow);
 
@@ -80,10 +80,10 @@ describe('Dependency Injection Cookbook', () => {
     });
 
     describe('in Parent Finder', () => {
-      let cathy1 = element(by.css('alex cathy'));
+      const cathy1 = element(by.css('alex cathy'));
-      let craig1 = element(by.css('alex craig'));
+      const craig1 = element(by.css('alex craig'));
-      let carol1 = element(by.css('alex carol p'));
+      const carol1 = element(by.css('alex carol p'));
-      let carol2 = element(by.css('barry carol p'));
+      const carol2 = element(by.css('barry carol p'));
 
       it('"Cathy" should find "Alex" via the component class', () => {
         expect(cathy1.getText()).toContain('Found Alex via the component');

aio/content/examples/dependency-injection-in-action/src/app/hero-data.ts

@@ -3,7 +3,7 @@ import { Hero } from './hero';
 
 export class HeroData {
   createDb() {
-    let heroes = [
+    const heroes = [
       new Hero(1, 'Windstorm'),
       new Hero(2, 'Bombasto'),
       new Hero(3, 'Magneta'),

aio/content/examples/dependency-injection-in-action/src/app/user-context.service.ts

@@ -24,7 +24,7 @@ export class UserContextService {
   // #enddocregion ctor, injectables
 
   loadUser(userId: number) {
-    let user = this.userService.getUserById(userId);
+    const user = this.userService.getUserById(userId);
     this.name = user.name;
     this.role = user.role;
 

aio/content/examples/dependency-injection/e2e/src/app.e2e-spec.ts

@@ -138,15 +138,15 @@ describe('Dependency Injection Tests', () => {
     });
 
     it('unauthorized user should have multiple unauthorized heroes', () => {
-      let heroes = element.all(by.css('#unauthorized app-hero-list div'));
+      const heroes = element.all(by.css('#unauthorized app-hero-list div'));
       expect(heroes.count()).toBeGreaterThan(0);
     });
 
     it('unauthorized user should have no secret heroes', () => {
-      let heroes = element.all(by.css('#unauthorized app-hero-list div'));
+      const heroes = element.all(by.css('#unauthorized app-hero-list div'));
       expect(heroes.count()).toBeGreaterThan(0);
 
-      let filteredHeroes = heroes.filter((elem: ElementFinder, index: number) => {
+      const filteredHeroes = heroes.filter((elem: ElementFinder, index: number) => {
         return elem.getText().then((text: string) => /secret/.test(text));
       });
 
@@ -160,7 +160,7 @@ describe('Dependency Injection Tests', () => {
     describe('after button click', () => {
 
       beforeAll((done: any) => {
-        let buttonEle = element.all(by.cssContainingText('button', 'Next User')).get(0);
+        const buttonEle = element.all(by.cssContainingText('button', 'Next User')).get(0);
         buttonEle.click().then(done, done);
       });
 
@@ -170,20 +170,20 @@ describe('Dependency Injection Tests', () => {
       });
 
       it('authorized user should have multiple authorized heroes ', () => {
-        let heroes = element.all(by.css('#authorized app-hero-list div'));
+        const heroes = element.all(by.css('#authorized app-hero-list div'));
         expect(heroes.count()).toBeGreaterThan(0);
       });
 
       it('authorized user should have multiple authorized heroes with tree-shakeable HeroesService', () => {
-        let heroes = element.all(by.css('#tspAuthorized app-hero-list div'));
+        const heroes = element.all(by.css('#tspAuthorized app-hero-list div'));
         expect(heroes.count()).toBeGreaterThan(0);
       });
 
       it('authorized user should have secret heroes', () => {
-        let heroes = element.all(by.css('#authorized app-hero-list div'));
+        const heroes = element.all(by.css('#authorized app-hero-list div'));
         expect(heroes.count()).toBeGreaterThan(0);
 
-        let filteredHeroes = heroes.filter((elem: ElementFinder, index: number) => {
+        const filteredHeroes = heroes.filter((elem: ElementFinder, index: number) => {
          return elem.getText().then((text: string) => /secret/.test(text));
         });
 

aio/content/examples/dependency-injection/src/app/car/car-creations.ts

@@ -7,7 +7,7 @@ import { Car, Engine, Tires } from './car';
 export function simpleCar() {
   // #docregion car-ctor-instantiation
   // Simple car with 4 cylinders and Flintstone tires.
-  let car = new Car(new Engine(), new Tires());
+  const car = new Car(new Engine(), new Tires());
   // #enddocregion car-ctor-instantiation
   car.description = 'Simple';
   return car;
@@ -24,8 +24,8 @@ class Engine2 {
 export function superCar() {
   // #docregion car-ctor-instantiation-with-param
   // Super car with 12 cylinders and Flintstone tires.
-  let bigCylinders = 12;
+  const bigCylinders = 12;
-  let car = new Car(new Engine2(bigCylinders), new Tires());
+  const car = new Car(new Engine2(bigCylinders), new Tires());
   // #enddocregion car-ctor-instantiation-with-param
   car.description = 'Super';
   return car;
@@ -40,7 +40,7 @@ class MockTires  extends Tires  { make = 'YokoGoodStone'; }
 export function testCar() {
   // #docregion car-ctor-instantiation-with-mocks
   // Test car with 8 cylinders and YokoGoodStone tires.
-  let car = new Car(new MockEngine(), new MockTires());
+  const car = new Car(new MockEngine(), new MockTires());
   // #enddocregion car-ctor-instantiation-with-mocks
   car.description = 'Test';
   return car;

aio/content/examples/dependency-injection/src/app/car/car-factory.ts

@@ -4,7 +4,7 @@ import { Engine, Tires, Car } from './car';
 // BAD pattern!
 export class CarFactory {
   createCar() {
-    let car = new Car(this.createEngine(), this.createTires());
+    const car = new Car(this.createEngine(), this.createTires());
     car.description = 'Factory';
     return car;
   }

aio/content/examples/dependency-injection/src/app/car/car-injector.ts

@@ -26,14 +26,14 @@ export function useInjector() {
     ]
   });
   // #docregion injector-call
-  let car = injector.get(Car);
+  const car = injector.get(Car);
   // #enddocregion injector-call, injector-create-and-call
   car.description = 'Injector';
 
   injector = Injector.create({
     providers: [{ provide: Logger, deps: [] }]
   });
-  let logger = injector.get(Logger);
+  const logger = injector.get(Logger);
   logger.log('Injector car.drive() said: ' + car.drive());
   return car;
 }

aio/content/examples/dependency-injection/src/app/heroes/hero.service.provider.ts

@@ -5,7 +5,7 @@ import { Logger } from '../logger.service';
 import { UserService } from '../user.service';
 
 // #docregion factory
-let heroServiceFactory = (logger: Logger, userService: UserService) => {
+const heroServiceFactory = (logger: Logger, userService: UserService) => {
   return new HeroService(logger, userService.user.isAuthorized);
 };
 // #enddocregion factory

aio/content/examples/dependency-injection/src/app/heroes/hero.service.ts

@@ -17,7 +17,7 @@ export class HeroService {
     private isAuthorized: boolean) { }
 
   getHeroes() {
-    let auth = this.isAuthorized ? 'authorized ' : 'unauthorized';
+    const auth = this.isAuthorized ? 'authorized ' : 'unauthorized';
     this.logger.log(`Getting heroes for ${auth} user.`);
     return HEROES.filter(hero => this.isAuthorized || !hero.isSecret);
   }

aio/content/examples/dependency-injection/src/app/injector.component.ts

@@ -36,7 +36,7 @@ export class InjectorComponent implements OnInit {
   }
 
   get rodent() {
-    let rousDontExist = `R.O.U.S.'s? I don't think they exist!`;
+    const rousDontExist = `R.O.U.S.'s? I don't think they exist!`;
     return this.injector.get(ROUS, rousDontExist);
   }
 }

aio/content/examples/dependency-injection/src/app/providers.component.ts

@@ -76,7 +76,7 @@ export class EvenBetterLogger extends Logger {
   constructor(private userService: UserService) { super(); }
 
   log(message: string) {
-    let name = this.userService.user.name;
+    const name = this.userService.user.name;
     super.log(`Message to ${name}: ${message}`);
   }
 }
@@ -237,7 +237,7 @@ export class Provider9Component implements OnInit {
 import { Optional } from '@angular/core';
 // #enddocregion import-optional
 
-let someMessage = 'Hello from the injected logger';
+const someMessage = 'Hello from the injected logger';
 
 @Component({
   selector: 'provider-10',

aio/content/examples/dependency-injection/src/app/user.service.ts

@@ -8,8 +8,8 @@ export class User {
 }
 
 // TODO: get the user; don't 'new' it.
-let alice = new User('Alice', true);
+const alice = new User('Alice', true);
-let bob = new User('Bob', false);
+const bob = new User('Bob', false);
 
 @Injectable({
   providedIn: 'root'

aio/content/examples/displaying-data/e2e/src/app.e2e-spec.ts

@@ -1,8 +1,8 @@
 import { browser, element, by } from 'protractor';
 
 describe('Displaying Data Tests', () => {
-  let title = 'Tour of Heroes';
+  const title = 'Tour of Heroes';
-  let defaultHero = 'Windstorm';
+  const defaultHero = 'Windstorm';
 
   beforeAll(() => {
     browser.get('');
@@ -17,7 +17,7 @@ describe('Displaying Data Tests', () => {
   });
 
   it('should have heroes', () => {
-    let heroEls = element.all(by.css('li'));
+    const heroEls = element.all(by.css('li'));
     expect(heroEls.count()).not.toBe(0, 'should have heroes');
   });
 

aio/content/examples/docs-style-guide/e2e/src/app.e2e-spec.ts

@@ -1,7 +1,7 @@
 import { browser, element, by } from 'protractor';
 
 describe('Docs Style Guide', () => {
-  let title = 'Authors Style Guide Sample';
+  const title = 'Authors Style Guide Sample';
 
   beforeAll(() => {
     browser.get('');

aio/content/examples/dynamic-component-loader/e2e/src/app.e2e-spec.ts

@@ -8,9 +8,9 @@ describe('Dynamic Component Loader', () => {
   });
 
   it('should load ad banner', () => {
-    let headline = element(by.xpath("//h4[text()='Featured Hero Profile']"));
+    const headline = element(by.xpath("//h4[text()='Featured Hero Profile']"));
-    let name = element(by.xpath("//h3[text()='Bombasto']"));
+    const name = element(by.xpath("//h3[text()='Bombasto']"));
-    let bio = element(by.xpath("//p[text()='Brave as they come']"));
+    const bio = element(by.xpath("//p[text()='Brave as they come']"));
 
     expect(name).toBeDefined();
     expect(headline).toBeDefined();

aio/content/examples/dynamic-form/e2e/src/app.e2e-spec.ts

@@ -8,17 +8,17 @@ describe('Dynamic Form', () => {
     });
 
     it('should submit form', () => {
-      let firstNameElement = element.all(by.css('input[id=firstName]')).get(0);
+      const firstNameElement = element.all(by.css('input[id=firstName]')).get(0);
       expect(firstNameElement.getAttribute('value')).toEqual('Bombasto');
 
-      let emailElement = element.all(by.css('input[id=emailAddress]')).get(0);
+      const emailElement = element.all(by.css('input[id=emailAddress]')).get(0);
-      let email = 'test@test.com';
+      const email = 'test@test.com';
       emailElement.sendKeys(email);
       expect(emailElement.getAttribute('value')).toEqual(email);
 
       element(by.css('select option[value="solid"]')).click();
 
-      let saveButton = element.all(by.css('button')).get(0);
+      const saveButton = element.all(by.css('button')).get(0);
       saveButton.click().then(() => {
         expect(element(by.xpath("//strong[contains(text(),'Saved the following values')]")).isPresent()).toBe(true);
       });

aio/content/examples/dynamic-form/src/app/question-control.service.ts

@@ -9,7 +9,7 @@ export class QuestionControlService {
   constructor() { }
 
   toFormGroup(questions: QuestionBase<string>[] ) {
-    let group: any = {};
+    const group: any = {};
 
     questions.forEach(question => {
       group[question.key] = question.required ? new FormControl(question.value || '', Validators.required)

aio/content/examples/dynamic-form/src/app/question.service.ts

@@ -12,7 +12,7 @@ export class QuestionService {
   // TODO: get from a remote source of question metadata
   getQuestions() {
 
-    let questions: QuestionBase<string>[] = [
+    const questions: QuestionBase<string>[] = [
 
       new DropdownQuestion({
         key: 'brave',

aio/content/examples/event-binding/e2e/src/app.e2e-spec.ts

@@ -6,12 +6,12 @@ describe('Event binding example', () => {
     browser.get('');
   });
 
-  let saveButton = element.all(by.css('button')).get(0);
+  const saveButton = element.all(by.css('button')).get(0);
-  let onSaveButton = element.all(by.css('button')).get(1);
+  const onSaveButton = element.all(by.css('button')).get(1);
-  let myClick = element.all(by.css('button')).get(2);
+  const myClick = element.all(by.css('button')).get(2);
-  let deleteButton = element.all(by.css('button')).get(3);
+  const deleteButton = element.all(by.css('button')).get(3);
-  let saveNoProp = element.all(by.css('button')).get(4);
+  const saveNoProp = element.all(by.css('button')).get(4);
-  let saveProp = element.all(by.css('button')).get(5);
+  const saveProp = element.all(by.css('button')).get(5);
 
 
   it('should display Event Binding with Angular', () => {
@@ -28,8 +28,8 @@ describe('Event binding example', () => {
   });
 
   it('should support user input', () => {
-    let input = element(by.css('input'));
+    const input = element(by.css('input'));
-    let bindingResult = element.all(by.css('h4')).get(1);
+    const bindingResult = element.all(by.css('h4')).get(1);
     expect(bindingResult.getText()).toEqual('Result: teapot');
     input.sendKeys('abc');
     expect(bindingResult.getText()).toEqual('Result: teapotabc');
@@ -42,8 +42,8 @@ describe('Event binding example', () => {
   });
 
   it('should show two alerts', async () => {
-    let parentDiv = element.all(by.css('.parent-div'));
+    const parentDiv = element.all(by.css('.parent-div'));
-    let childDiv = element.all(by.css('div > div')).get(1);
+    const childDiv = element.all(by.css('div > div')).get(1);
     await parentDiv.click();
     browser.switchTo().alert().accept();
     expect(childDiv.getText()).toEqual('Click me too! (child)');

aio/content/examples/form-validation/e2e/src/app.e2e-spec.ts

@@ -50,8 +50,8 @@ let page: {
 };
 
 function getPage(sectionTag: string) {
-  let section = element(by.css(sectionTag));
+  const section = element(by.css(sectionTag));
-  let buttons = section.all(by.css('button'));
+  const buttons = section.all(by.css('button'));
 
   page = {
     section,

aio/content/examples/forms-overview/src/app/shared/utils.ts

@@ -1,5 +1,5 @@
 export function createNewEvent(eventName: string, bubbles = false, cancelable = false) {
-  let evt = document.createEvent('CustomEvent');
+  const evt = document.createEvent('CustomEvent');
   evt.initCustomEvent(eventName, bubbles, cancelable, null);
   return evt;
 }

aio/content/examples/forms/e2e/src/app.e2e-spec.ts

@@ -12,49 +12,49 @@ describe('Forms Tests', () => {
 
 
   it('should not display message before submit', () => {
-    let ele = element(by.css('h2'));
+    const ele = element(by.css('h2'));
     expect(ele.isDisplayed()).toBe(false);
   });
 
   it('should hide form after submit', () => {
-    let ele = element.all(by.css('h1')).get(0);
+    const ele = element.all(by.css('h1')).get(0);
     expect(ele.isDisplayed()).toBe(true);
-    let b = element.all(by.css('button[type=submit]')).get(0);
+    const b = element.all(by.css('button[type=submit]')).get(0);
     b.click().then(() => {
       expect(ele.isDisplayed()).toBe(false);
     });
   });
 
   it('should display message after submit', () => {
-    let b = element.all(by.css('button[type=submit]')).get(0);
+    const b = element.all(by.css('button[type=submit]')).get(0);
     b.click().then(() => {
       expect(element(by.css('h2')).getText()).toContain('You submitted the following');
     });
   });
 
   it('should hide form after submit', () => {
-    let alterEgoEle = element.all(by.css('input[name=alterEgo]')).get(0);
+    const alterEgoEle = element.all(by.css('input[name=alterEgo]')).get(0);
     expect(alterEgoEle.isDisplayed()).toBe(true);
-    let submitButtonEle = element.all(by.css('button[type=submit]')).get(0);
+    const submitButtonEle = element.all(by.css('button[type=submit]')).get(0);
     submitButtonEle.click().then(() => {
       expect(alterEgoEle.isDisplayed()).toBe(false);
     });
   });
 
   it('should reflect submitted data after submit', () => {
-    let test = 'testing 1 2 3';
+    const test = 'testing 1 2 3';
     let newValue: string;
-    let alterEgoEle = element.all(by.css('input[name=alterEgo]')).get(0);
+    const alterEgoEle = element.all(by.css('input[name=alterEgo]')).get(0);
     alterEgoEle.getAttribute('value').then((value: string) => {
       alterEgoEle.sendKeys(test);
       newValue = value + test;
       expect(alterEgoEle.getAttribute('value')).toEqual(newValue);
-      let b = element.all(by.css('button[type=submit]')).get(0);
+      const b = element.all(by.css('button[type=submit]')).get(0);
       return b.click();
     }).then(() => {
-      let alterEgoTextEle = element(by.cssContainingText('div', 'Alter Ego'));
+      const alterEgoTextEle = element(by.cssContainingText('div', 'Alter Ego'));
       expect(alterEgoTextEle.isPresent()).toBe(true, 'cannot locate "Alter Ego" label');
-      let divEle = element(by.cssContainingText('div', newValue));
+      const divEle = element(by.cssContainingText('div', newValue));
       expect(divEle.isPresent()).toBe(true, 'cannot locate div with this text: ' + newValue);
     });
   });

aio/content/examples/forms/src/app/hero-form/hero-form.component.ts

@@ -35,7 +35,7 @@ export class HeroFormComponent {
 
   skyDog(): Hero {
     // #docregion SkyDog
-    let myHero =  new Hero(42, 'SkyDog',
+    const myHero =  new Hero(42, 'SkyDog',
                            'Fetch any object at any distance',
                            'Leslie Rollover');
     console.log('My hero is called ' + myHero.name); // "My hero is called SkyDog"

aio/content/examples/hierarchical-dependency-injection/e2e/src/app.e2e-spec.ts

@@ -7,7 +7,7 @@ describe('Hierarchical dependency injection', () => {
   });
 
   describe('Heroes Scenario', () => {
-    let page = {
+    const page = {
       heroName: '',
       income: '',
 

aio/content/examples/http/e2e/src/app.e2e-spec.ts

@@ -24,7 +24,7 @@ const page = {
   uploadMessage: element(by.css('app-uploader p'))
 };
 
-let checkLogForMessage = (message: string) => {
+const checkLogForMessage = (message: string) => {
   expect(page.logList.getText()).toContain(message);
 };
 

aio/content/examples/http/src/testing/http-client.spec.ts

@@ -90,7 +90,7 @@ describe('HttpClient testing', () => {
   });
 
   it('can test multiple requests', () => {
-    let testData: Data[] = [
+    const testData: Data[] = [
       { name: 'bob' }, { name: 'carol' },
       { name: 'ted' }, { name: 'alice' }
     ];

aio/content/examples/inputs-outputs/e2e/src/app.e2e-spec.ts

@@ -18,43 +18,43 @@ describe('Inputs and Outputs', () => {
   }
 
   it('should have title Inputs and Outputs', () => {
-    let title = element.all(by.css('h1')).get(0);
+    const title = element.all(by.css('h1')).get(0);
     expect(title.getText()).toEqual('Inputs and Outputs');
   });
 
   it('should add 123 to the parent list', async () => {
-    let addToParentButton = element.all(by.css('button')).get(0);
+    const addToParentButton = element.all(by.css('button')).get(0);
-    let addToListInput = element.all(by.css('input')).get(0);
+    const addToListInput = element.all(by.css('input')).get(0);
-    let addedItem = element.all(by.css('li')).get(4);
+    const addedItem = element.all(by.css('li')).get(4);
     await addToListInput.sendKeys('123');
     await addToParentButton.click();
     expect(addedItem.getText()).toEqual('123');
   });
 
   it('should delete item', async () => {
-    let deleteButton = element.all(by.css('button')).get(1);
+    const deleteButton = element.all(by.css('button')).get(1);
     const contents = 'Child';
     await deleteButton.click();
     await logChecker(deleteButton, contents);
   });
 
   it('should log buy the item', async () => {
-    let buyButton = element.all(by.css('button')).get(2);
+    const buyButton = element.all(by.css('button')).get(2);
     const contents = 'Child';
     await buyButton.click();
     await logChecker(buyButton, contents);
   });
 
   it('should save item for later', async () => {
-    let saveButton = element.all(by.css('button')).get(3);
+    const saveButton = element.all(by.css('button')).get(3);
     const contents = 'Child';
     await saveButton.click();
     await logChecker(saveButton, contents);
   });
 
   it('should add item to wishlist', async () => {
-    let addToParentButton = element.all(by.css('button')).get(4);
+    const addToParentButton = element.all(by.css('button')).get(4);
-    let addedItem = element.all(by.css('li')).get(6);
+    const addedItem = element.all(by.css('li')).get(6);
     await addToParentButton.click();
     expect(addedItem.getText()).toEqual('Television');
   });

aio/content/examples/interpolation/e2e/src/app.e2e-spec.ts

@@ -27,8 +27,8 @@ describe('Interpolation e2e tests', () => {
   });
 
   it('should display two pictures', () => {
-    let pottedPlant = element.all(by.css('img')).get(0);
+    const pottedPlant = element.all(by.css('img')).get(0);
-    let lamp = element.all(by.css('img')).get(1);
+    const lamp = element.all(by.css('img')).get(1);
 
     expect(pottedPlant.getAttribute('src')).toContain('potted-plant');
     expect(pottedPlant.isDisplayed()).toBe(true);
@@ -38,8 +38,8 @@ describe('Interpolation e2e tests', () => {
   });
 
   it('should support user input', () => {
-    let input = element(by.css('input'));
+    const input = element(by.css('input'));
-    let label = element(by.css('label'));
+    const label = element(by.css('label'));
     expect(label.getText()).toEqual('Type something:');
     input.sendKeys('abc');
     expect(label.getText()).toEqual('Type something: abc');

aio/content/examples/lazy-loading-ngmodules/e2e/src/app.e2e-spec.ts

@@ -24,7 +24,7 @@ describe('providers App', () => {
     });
 
     it('should show customers when the button is clicked', () => {
-        let customersMessage = element(by.css('app-customers > p'));
+        const customersMessage = element(by.css('app-customers > p'));
         expect(customersMessage.getText()).toBe('customers works!');
     });
 
@@ -36,7 +36,7 @@ describe('providers App', () => {
     });
 
     it('should show orders when the button is clicked', () => {
-        let ordersMessage = element(by.css('app-orders > p'));
+        const ordersMessage = element(by.css('app-orders > p'));
         expect(ordersMessage.getText()).toBe('orders works!');
     });
 

aio/content/examples/lifecycle-hooks/e2e/src/app.e2e-spec.ts

@@ -13,11 +13,11 @@ describe('Lifecycle hooks', () => {
   });
 
   it('should support peek-a-boo', async () => {
-    let pabComp = element(by.css('peek-a-boo-parent peek-a-boo'));
+    const pabComp = element(by.css('peek-a-boo-parent peek-a-boo'));
     expect(pabComp.isPresent()).toBe(false, 'should not be able to find the "peek-a-boo" component');
 
-    let pabButton = element.all(by.css('peek-a-boo-parent button')).get(0);
+    const pabButton = element.all(by.css('peek-a-boo-parent button')).get(0);
-    let updateHeroButton = element.all(by.css('peek-a-boo-parent button')).get(1);
+    const updateHeroButton = element.all(by.css('peek-a-boo-parent button')).get(1);
     expect(pabButton.getText()).toContain('Create Peek');
 
     await pabButton.click();
@@ -35,12 +35,12 @@ describe('Lifecycle hooks', () => {
   });
 
   it('should support OnChanges hook', () => {
-    let onChangesViewEle = element.all(by.css('on-changes div')).get(0);
+    const onChangesViewEle = element.all(by.css('on-changes div')).get(0);
-    let inputEles = element.all(by.css('on-changes-parent input'));
+    const inputEles = element.all(by.css('on-changes-parent input'));
-    let heroNameInputEle = inputEles.get(1);
+    const heroNameInputEle = inputEles.get(1);
-    let powerInputEle = inputEles.get(0);
+    const powerInputEle = inputEles.get(0);
-    let titleEle = onChangesViewEle.element(by.css('p'));
+    const titleEle = onChangesViewEle.element(by.css('p'));
-    let changeLogEles = onChangesViewEle.all(by.css('div'));
+    const changeLogEles = onChangesViewEle.all(by.css('div'));
 
     expect(titleEle.getText()).toContain('Windstorm can sing');
     expect(changeLogEles.count()).toEqual(2, 'should start with 2 messages');
@@ -54,12 +54,12 @@ describe('Lifecycle hooks', () => {
   });
 
   it('should support DoCheck hook', async () => {
-    let doCheckViewEle = element.all(by.css('do-check div')).get(0);
+    const doCheckViewEle = element.all(by.css('do-check div')).get(0);
-    let inputEles = element.all(by.css('do-check-parent input'));
+    const inputEles = element.all(by.css('do-check-parent input'));
-    let heroNameInputEle = inputEles.get(1);
+    const heroNameInputEle = inputEles.get(1);
-    let powerInputEle = inputEles.get(0);
+    const powerInputEle = inputEles.get(0);
-    let titleEle = doCheckViewEle.element(by.css('p'));
+    const titleEle = doCheckViewEle.element(by.css('p'));
-    let changeLogEles = doCheckViewEle.all(by.css('div'));
+    const changeLogEles = doCheckViewEle.all(by.css('div'));
     let logCount: number;
 
     expect(titleEle.getText()).toContain('Windstorm can sing');
@@ -82,11 +82,11 @@ describe('Lifecycle hooks', () => {
   });
 
   it('should support AfterView hooks', async () => {
-    let parentEle = element(by.tagName('after-view-parent'));
+    const parentEle = element(by.tagName('after-view-parent'));
-    let buttonEle = parentEle.element(by.tagName('button')); // Reset
+    const buttonEle = parentEle.element(by.tagName('button')); // Reset
-    let commentEle = parentEle.element(by.className('comment'));
+    const commentEle = parentEle.element(by.className('comment'));
-    let logEles = parentEle.all(by.css('h4 ~ div'));
+    const logEles = parentEle.all(by.css('h4 ~ div'));
-    let childViewInputEle = parentEle.element(by.css('app-child-view input'));
+    const childViewInputEle = parentEle.element(by.css('app-child-view input'));
     let logCount: number;
 
     expect(childViewInputEle.getAttribute('value')).toContain('Magneta');
@@ -99,7 +99,7 @@ describe('Lifecycle hooks', () => {
     expect(commentEle.isPresent()).toBe(true, 'should have comment because >10 chars');
     expect(commentEle.getText()).toContain('long name');
 
-    let count = await logEles.count();
+    const count = await logEles.count();
     expect(logCount + 7).toBeGreaterThan(count - 3, '7 additional log messages should have been added');
     expect(logCount + 7).toBeLessThan(count + 3, '7 additional log messages should have been added');
 
@@ -109,18 +109,18 @@ describe('Lifecycle hooks', () => {
   });
 
   it('should support AfterContent hooks', async () => {
-    let parentEle = element(by.tagName('after-content-parent'));
+    const parentEle = element(by.tagName('after-content-parent'));
-    let buttonEle = parentEle.element(by.tagName('button')); // Reset
+    const buttonEle = parentEle.element(by.tagName('button')); // Reset
-    let commentEle = parentEle.element(by.className('comment'));
+    const commentEle = parentEle.element(by.className('comment'));
-    let logEles = parentEle.all(by.css('h4 ~ div'));
+    const logEles = parentEle.all(by.css('h4 ~ div'));
-    let childViewInputEle = parentEle.element(by.css('app-child input'));
+    const childViewInputEle = parentEle.element(by.css('app-child input'));
     let logCount = await logEles.count();
 
     expect(childViewInputEle.getAttribute('value')).toContain('Magneta');
     expect(commentEle.isPresent()).toBe(false, 'comment should not be in DOM');
 
     await sendKeys(childViewInputEle, '-test-');
-    let count = await logEles.count();
+    const count = await logEles.count();
     expect(childViewInputEle.getAttribute('value')).toContain('-test-');
     expect(commentEle.isPresent()).toBe(true, 'should have comment because >10 chars');
     expect(commentEle.getText()).toContain('long name');
@@ -132,11 +132,11 @@ describe('Lifecycle hooks', () => {
   });
 
   it('should support spy\'s OnInit & OnDestroy hooks', async () => {
-    let inputEle = element(by.css('spy-parent input'));
+    const inputEle = element(by.css('spy-parent input'));
-    let addHeroButtonEle = element(by.cssContainingText('spy-parent button', 'Add Hero'));
+    const addHeroButtonEle = element(by.cssContainingText('spy-parent button', 'Add Hero'));
-    let resetHeroesButtonEle = element(by.cssContainingText('spy-parent button', 'Reset Heroes'));
+    const resetHeroesButtonEle = element(by.cssContainingText('spy-parent button', 'Reset Heroes'));
-    let heroEles = element.all(by.css('spy-parent div[mySpy'));
+    const heroEles = element.all(by.css('spy-parent div[mySpy'));
-    let logEles = element.all(by.css('spy-parent h4 ~ div'));
+    const logEles = element.all(by.css('spy-parent h4 ~ div'));
 
     expect(heroEles.count()).toBe(2, 'should have two heroes displayed');
     expect(logEles.count()).toBe(2, 'should have two log entries');
@@ -153,10 +153,10 @@ describe('Lifecycle hooks', () => {
   });
 
   it('should support "spy counter"', async () => {
-    let updateCounterButtonEle = element(by.cssContainingText('counter-parent button', 'Update'));
+    const updateCounterButtonEle = element(by.cssContainingText('counter-parent button', 'Update'));
-    let resetCounterButtonEle = element(by.cssContainingText('counter-parent button', 'Reset'));
+    const resetCounterButtonEle = element(by.cssContainingText('counter-parent button', 'Reset'));
-    let textEle = element(by.css('counter-parent app-counter > div'));
+    const textEle = element(by.css('counter-parent app-counter > div'));
-    let logEles = element.all(by.css('counter-parent h4 ~ div'));
+    const logEles = element.all(by.css('counter-parent h4 ~ div'));
 
     expect(textEle.getText()).toContain('Counter = 0');
     expect(logEles.count()).toBe(2, 'should start with two log entries');

aio/content/examples/lifecycle-hooks/src/app/after-content.component.ts

@@ -67,8 +67,8 @@ export class AfterContentComponent implements AfterContentChecked, AfterContentI
   }
 
   private logIt(method: string) {
-    let child = this.contentChild;
+    const child = this.contentChild;
-    let message = `${method}: ${child ? child.hero : 'no'} child content`;
+    const message = `${method}: ${child ? child.hero : 'no'} child content`;
     this.logger.log(message);
   }
 // #docregion hooks

aio/content/examples/lifecycle-hooks/src/app/after-view.component.ts

@@ -67,7 +67,7 @@ export class AfterViewComponent implements  AfterViewChecked, AfterViewInit {
   // #docregion do-something
   // This surrogate for real business logic sets the `comment`
   private doSomething() {
-    let c = this.viewChild.hero.length > 10 ? `That's a long name` : '';
+    const c = this.viewChild.hero.length > 10 ? `That's a long name` : '';
     if (c !== this.comment) {
       // Wait a tick because the component's view has already been checked
       this.logger.tick_then(() => this.comment = c);
@@ -76,8 +76,8 @@ export class AfterViewComponent implements  AfterViewChecked, AfterViewInit {
   // #enddocregion do-something
 
   private logIt(method: string) {
-    let child = this.viewChild;
+    const child = this.viewChild;
-    let message = `${method}: ${child ? child.hero : 'no'} child view`;
+    const message = `${method}: ${child ? child.hero : 'no'} child view`;
     this.logger.log(message);
   }
   // #docregion hooks

aio/content/examples/lifecycle-hooks/src/app/counter.component.ts

@@ -31,9 +31,9 @@ export class MyCounterComponent implements OnChanges {
     }
 
     // A change to `counter` is the only change we care about
-    let chng = changes.counter;
+    const chng = changes.counter;
-    let cur = chng.currentValue;
+    const cur = chng.currentValue;
-    let prev = JSON.stringify(chng.previousValue); // first time is {}; after is integer
+    const prev = JSON.stringify(chng.previousValue); // first time is {}; after is integer
     this.changeLog.push(`counter: currentValue = ${cur}, previousValue = ${prev}`);
   }
 }

aio/content/examples/lifecycle-hooks/src/app/do-check.component.ts

@@ -51,8 +51,8 @@ export class DoCheckComponent implements DoCheck {
         this.noChangeCount = 0;
     } else {
         // log that hook was called when there was no relevant change.
-        let count = this.noChangeCount += 1;
+        const count = this.noChangeCount += 1;
-        let noChangeMsg = `DoCheck called ${count}x when no change to hero or power`;
+        const noChangeMsg = `DoCheck called ${count}x when no change to hero or power`;
         if (count === 1) {
           // add new "no change" message
           this.changeLog.push(noChangeMsg);

aio/content/examples/lifecycle-hooks/src/app/on-changes.component.ts

@@ -34,10 +34,10 @@ export class OnChangesComponent implements OnChanges {
 
   // #docregion ng-on-changes
   ngOnChanges(changes: SimpleChanges) {
-    for (let propName in changes) {
+    for (const propName in changes) {
-      let chng = changes[propName];
+      const chng = changes[propName];
-      let cur  = JSON.stringify(chng.currentValue);
+      const cur  = JSON.stringify(chng.currentValue);
-      let prev = JSON.stringify(chng.previousValue);
+      const prev = JSON.stringify(chng.previousValue);
       this.changeLog.push(`${propName}: currentValue = ${cur}, previousValue = ${prev}`);
     }
   }

aio/content/examples/lifecycle-hooks/src/app/peek-a-boo.component.ts

@@ -48,16 +48,16 @@ export class PeekABooComponent extends PeekABooDirective implements
   constructor(logger: LoggerService) {
     super(logger);
 
-    let is = this.name ? 'is' : 'is not';
+    const is = this.name ? 'is' : 'is not';
     this.logIt(`name ${is} known at construction`);
   }
 
   // only called for/if there is an @input variable set by parent.
   ngOnChanges(changes: SimpleChanges) {
-    let changesMsgs: string[] = [];
+    const changesMsgs: string[] = [];
-    for (let propName in changes) {
+    for (const propName in changes) {
       if (propName === 'name') {
-        let name = changes.name.currentValue;
+        const name = changes.name.currentValue;
         changesMsgs.push(`name ${this.verb} to "${name}"`);
       } else {
         changesMsgs.push(propName + ' ' + this.verb);

aio/content/examples/ngmodules/src/app/contact/contact.component.ts

@@ -46,7 +46,7 @@ export class ContactComponent implements OnInit {
   }
 
   onSubmit() {
-    let newName = this.contactForm.get('name').value;
+    const newName = this.contactForm.get('name').value;
     this.displayMessage('Saved ' + newName);
     this.contact.name = newName;
   }

aio/content/examples/ngmodules/src/app/customers/customers-detail.component.ts

@@ -25,7 +25,7 @@ export class CustomersDetailComponent implements OnInit {
     private customersService: CustomersService) { }
 
   ngOnInit() {
-    let id = parseInt(this.route.snapshot.paramMap.get('id'), 10);
+    const id = parseInt(this.route.snapshot.paramMap.get('id'), 10);
     this.customersService.getCustomer(id).subscribe(customer => this.customer = customer);
   }
 }

aio/content/examples/pipes/e2e/src/app.e2e-spec.ts

@@ -26,13 +26,13 @@ describe('Pipes', () => {
   });
 
   it('should be able to toggle birthday formats', () => {
-    let birthDayEle = element(by.css('app-hero-birthday2 > p'));
+    const birthDayEle = element(by.css('app-hero-birthday2 > p'));
     if (angularVersion.indexOf('4.') === 0) { // Breaking change between v4 and v5 (https://github.com/angular/angular/commit/079d884)
       expect(birthDayEle.getText()).toEqual(`The hero's birthday is 4/15/1988`);
     } else {
       expect(birthDayEle.getText()).toEqual(`The hero's birthday is 4/15/88`);
     }
-    let buttonEle = element(by.cssContainingText('app-hero-birthday2 > button', 'Toggle Format'));
+    const buttonEle = element(by.cssContainingText('app-hero-birthday2 > button', 'Toggle Format'));
     expect(buttonEle.isDisplayed()).toBe(true);
     buttonEle.click().then(() => {
       expect(birthDayEle.getText()).toEqual(`The hero's birthday is Friday, April 15, 1988`);
@@ -40,7 +40,7 @@ describe('Pipes', () => {
   });
 
   it('should be able to chain and compose pipes', () => {
-    let chainedPipeEles = element.all(by.cssContainingText('app-root p', `The chained hero's`));
+    const chainedPipeEles = element.all(by.cssContainingText('app-root p', `The chained hero's`));
     expect(chainedPipeEles.count()).toBe(3, 'should have 3 chained pipe examples');
     expect(chainedPipeEles.get(0).getText()).toContain('APR 15, 1988');
     expect(chainedPipeEles.get(1).getText()).toContain('FRIDAY, APRIL 15, 1988');
@@ -48,15 +48,15 @@ describe('Pipes', () => {
   });
 
   it('should be able to use ExponentialStrengthPipe pipe', () => {
-    let ele = element(by.css('app-power-booster p'));
+    const ele = element(by.css('app-power-booster p'));
     expect(ele.getText()).toContain('Super power boost: 1024');
   });
 
   it('should be able to use the exponential calculator', () => {
-    let eles = element.all(by.css('app-power-boost-calculator input'));
+    const eles = element.all(by.css('app-power-boost-calculator input'));
-    let baseInputEle = eles.get(0);
+    const baseInputEle = eles.get(0);
-    let factorInputEle = eles.get(1);
+    const factorInputEle = eles.get(1);
-    let outputEle = element(by.css('app-power-boost-calculator p'));
+    const outputEle = element(by.css('app-power-boost-calculator p'));
     baseInputEle.clear().then(() => {
       baseInputEle.sendKeys('7');
       return factorInputEle.clear();
@@ -68,11 +68,11 @@ describe('Pipes', () => {
 
 
   it('should support flying heroes (pure) ', () => {
-    let nameEle = element(by.css('app-flying-heroes input[type="text"]'));
+    const nameEle = element(by.css('app-flying-heroes input[type="text"]'));
-    let canFlyCheckEle = element(by.css('app-flying-heroes #can-fly'));
+    const canFlyCheckEle = element(by.css('app-flying-heroes #can-fly'));
-    let mutateCheckEle = element(by.css('app-flying-heroes #mutate'));
+    const mutateCheckEle = element(by.css('app-flying-heroes #mutate'));
-    let resetEle = element(by.css('app-flying-heroes button'));
+    const resetEle = element(by.css('app-flying-heroes button'));
-    let flyingHeroesEle = element.all(by.css('app-flying-heroes #flyers div'));
+    const flyingHeroesEle = element.all(by.css('app-flying-heroes #flyers div'));
 
     expect(canFlyCheckEle.getAttribute('checked')).toEqual('true', 'should default to "can fly"');
     expect(mutateCheckEle.getAttribute('checked')).toEqual('true', 'should default to mutating array');
@@ -94,10 +94,10 @@ describe('Pipes', () => {
 
 
   it('should support flying heroes (impure) ', () => {
-    let nameEle = element(by.css('app-flying-heroes-impure input[type="text"]'));
+    const nameEle = element(by.css('app-flying-heroes-impure input[type="text"]'));
-    let canFlyCheckEle = element(by.css('app-flying-heroes-impure #can-fly'));
+    const canFlyCheckEle = element(by.css('app-flying-heroes-impure #can-fly'));
-    let mutateCheckEle = element(by.css('app-flying-heroes-impure #mutate'));
+    const mutateCheckEle = element(by.css('app-flying-heroes-impure #mutate'));
-    let flyingHeroesEle = element.all(by.css('app-flying-heroes-impure #flyers div'));
+    const flyingHeroesEle = element.all(by.css('app-flying-heroes-impure #flyers div'));
 
     expect(canFlyCheckEle.getAttribute('checked')).toEqual('true', 'should default to "can fly"');
     expect(mutateCheckEle.getAttribute('checked')).toEqual('true', 'should default to mutating array');

aio/content/examples/pipes/src/app/flying-heroes.component.ts

@@ -23,7 +23,7 @@ export class FlyingHeroesComponent {
   addHero(name: string) {
     name = name.trim();
     if (!name) { return; }
-    let hero = {name, canFly: this.canFly};
+    const hero = {name, canFly: this.canFly};
 // #enddocregion v1
     if (this.mutate) {
     // Pure pipe won't update display because heroes array reference is unchanged

aio/content/examples/router/e2e/src/app.e2e-spec.ts

@@ -100,7 +100,7 @@ describe('Router', () => {
     await page.heroesHref.click();
     await browser.sleep(600);
     const heroEle = page.heroesList.get(4);
-    let text = await heroEle.getText();
+    const text = await heroEle.getText();
     expect(text.length).toBeGreaterThan(0, 'hero item text length');
     // remove leading id from text
     const heroText = text.substr(text.indexOf(' ')).trim();
@@ -110,11 +110,11 @@ describe('Router', () => {
     expect(page.heroesList.count()).toBe(0, 'hero list count');
     expect(page.heroDetail.isPresent()).toBe(true, 'hero detail');
     expect(page.heroDetailTitle.getText()).toContain(heroText);
-    let inputEle = page.heroDetail.element(by.css('input'));
+    const inputEle = page.heroDetail.element(by.css('input'));
     await inputEle.sendKeys('-foo');
     expect(page.heroDetailTitle.getText()).toContain(heroText + '-foo');
 
-    let buttonEle = page.heroDetail.element(by.css('button'));
+    const buttonEle = page.heroDetail.element(by.css('button'));
     await buttonEle.click();
     await browser.sleep(600);
     expect(heroEle.getText()).toContain(heroText + '-foo');
@@ -166,7 +166,7 @@ describe('Router', () => {
     const page = getPageStruct();
     await page.crisisHref.click();
     let crisisEle = page.crisisList.get(index);
-    let text = await crisisEle.getText();
+    const text = await crisisEle.getText();
     expect(text.length).toBeGreaterThan(0, 'crisis item text length');
     // remove leading id from text
     const crisisText = text.substr(text.indexOf(' ')).trim();
@@ -174,10 +174,10 @@ describe('Router', () => {
     await crisisEle.click();
     expect(page.crisisDetail.isPresent()).toBe(true, 'crisis detail present');
     expect(page.crisisDetailTitle.getText()).toContain(crisisText);
-    let inputEle = page.crisisDetail.element(by.css('input'));
+    const inputEle = page.crisisDetail.element(by.css('input'));
     await inputEle.sendKeys('-foo');
 
-    let buttonEle = page.crisisDetail.element(by.buttonText(save ? 'Save' : 'Cancel'));
+    const buttonEle = page.crisisDetail.element(by.buttonText(save ? 'Save' : 'Cancel'));
     await buttonEle.click();
     crisisEle = page.crisisList.get(index);
     if (save) {

aio/content/examples/router/src/app/auth/auth.guard.2.ts

@@ -13,7 +13,7 @@ export class AuthGuard implements CanActivate {
   canActivate(
     next: ActivatedRouteSnapshot,
     state: RouterStateSnapshot): true|UrlTree {
-    let url: string = state.url;
+    const url: string = state.url;
 
     return this.checkLogin(url);
   }

aio/content/examples/router/src/app/auth/auth.guard.3.ts

@@ -18,7 +18,7 @@ export class AuthGuard implements CanActivate, CanActivateChild {
   canActivate(
     route: ActivatedRouteSnapshot,
     state: RouterStateSnapshot): true|UrlTree {
-    let url: string = state.url;
+    const url: string = state.url;
 
     return this.checkLogin(url);
   }

aio/content/examples/router/src/app/auth/auth.guard.4.ts

@@ -18,7 +18,7 @@ export class AuthGuard implements CanActivate, CanActivateChild {
   constructor(private authService: AuthService, private router: Router) {}
 
   canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): true|UrlTree {
-    let url: string = state.url;
+    const url: string = state.url;
 
     return this.checkLogin(url);
   }
@@ -34,11 +34,11 @@ export class AuthGuard implements CanActivate, CanActivateChild {
     this.authService.redirectUrl = url;
 
     // Create a dummy session id
-    let sessionId = 123456789;
+    const sessionId = 123456789;
 
     // Set our navigation extras object
     // that contains our global query params and fragment
-    let navigationExtras: NavigationExtras = {
+    const navigationExtras: NavigationExtras = {
       queryParams: { session_id: sessionId },
       fragment: 'anchor'
     };

aio/content/examples/router/src/app/auth/auth.guard.ts

@@ -17,7 +17,7 @@ export class AuthGuard implements CanActivate, CanActivateChild, CanLoad {
   constructor(private authService: AuthService, private router: Router) {}
 
   canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): boolean {
-    let url: string = state.url;
+    const url: string = state.url;
 
     return this.checkLogin(url);
   }
@@ -28,7 +28,7 @@ export class AuthGuard implements CanActivate, CanActivateChild, CanLoad {
 
 // #docregion, canLoad
   canLoad(route: Route): boolean {
-    let url = `/${route.path}`;
+    const url = `/${route.path}`;
 
     return this.checkLogin(url);
   }
@@ -41,11 +41,11 @@ export class AuthGuard implements CanActivate, CanActivateChild, CanLoad {
     this.authService.redirectUrl = url;
 
     // Create a dummy session id
-    let sessionId = 123456789;
+    const sessionId = 123456789;
 
     // Set our navigation extras object
     // that contains our global query params and fragment
-    let navigationExtras: NavigationExtras = {
+    const navigationExtras: NavigationExtras = {
       queryParams: { session_id: sessionId },
       fragment: 'anchor'
     };

aio/content/examples/router/src/app/auth/login/login.component.ts

@@ -32,7 +32,7 @@ export class LoginComponent {
         // #docregion preserve
         // Set our navigation extras object
         // that passes on our global query params and fragment
-        let navigationExtras: NavigationExtras = {
+        const navigationExtras: NavigationExtras = {
           queryParamsHandling: 'preserve',
           preserveFragment: true
         };

aio/content/examples/router/src/app/crisis-center/crisis-detail-resolver.service.ts

@@ -19,7 +19,7 @@ export class CrisisDetailResolverService implements Resolve<Crisis> {
   constructor(private cs: CrisisService, private router: Router) {}
 
   resolve(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Observable<Crisis> | Observable<never> {
-    let id = route.paramMap.get('id');
+    const id = route.paramMap.get('id');
 
     return this.cs.getCrisis(id).pipe(
       take(1),

aio/content/examples/router/src/app/crisis-center/crisis-detail/crisis-detail.component.1.ts

@@ -62,7 +62,7 @@ export class CrisisDetailComponent implements OnInit {
   }
 
   gotoCrises() {
-    let crisisId = this.crisis ? this.crisis.id : null;
+    const crisisId = this.crisis ? this.crisis.id : null;
     // Pass along the crisis id if available
     // so that the CrisisListComponent can select that crisis.
     // Add a totally useless `foo` parameter for kicks.

aio/content/examples/router/src/app/crisis-center/crisis-detail/crisis-detail.component.ts

@@ -56,7 +56,7 @@ export class CrisisDetailComponent implements OnInit {
   // #enddocregion canDeactivate
 
   gotoCrises() {
-    let crisisId = this.crisis ? this.crisis.id : null;
+    const crisisId = this.crisis ? this.crisis.id : null;
     // Pass along the crisis id if available
     // so that the CrisisListComponent can select that crisis.
     // Add a totally useless `foo` parameter for kicks.

aio/content/examples/router/src/app/crisis-center/crisis.service.ts

@@ -29,7 +29,7 @@ export class CrisisService {
   addCrisis(name: string) {
     name = name.trim();
     if (name) {
-      let crisis = { id: CrisisService.nextCrisisId++, name };
+      const crisis = { id: CrisisService.nextCrisisId++, name };
       CRISES.push(crisis);
       this.crises$.next(CRISES);
     }

aio/content/examples/router/src/app/heroes/hero-detail/hero-detail.component.2.ts

@@ -23,7 +23,7 @@ export class HeroDetailComponent implements OnInit  {
 
   // #docregion snapshot
   ngOnInit() {
-    let id = this.route.snapshot.paramMap.get('id');
+    const id = this.route.snapshot.paramMap.get('id');
 
     this.hero$ = this.service.getHero(id);
   }

aio/content/examples/router/src/app/heroes/hero-detail/hero-detail.component.3.ts

@@ -37,7 +37,7 @@ export class HeroDetailComponent implements OnInit {
 
   // #docregion gotoHeroes
   gotoHeroes(hero: Hero) {
-    let heroId = hero ? hero.id : null;
+    const heroId = hero ? hero.id : null;
     // Pass along the hero id if available
     // so that the HeroList component can select that hero.
     // Include a junk 'foo' property for fun.

aio/content/examples/router/src/app/heroes/hero-detail/hero-detail.component.ts

@@ -38,7 +38,7 @@ export class HeroDetailComponent implements OnInit {
 
   // #docregion redirect
   gotoHeroes(hero: Hero) {
-    let heroId = hero ? hero.id : null;
+    const heroId = hero ? hero.id : null;
     // Pass along the hero id if available
     // so that the HeroList component can select that hero.
     // Include a junk 'foo' property for fun.

aio/content/examples/security/e2e/src/app.e2e-spec.ts

@@ -4,32 +4,32 @@ describe('Security E2E Tests', () => {
   beforeAll(() => browser.get(''));
 
   it('sanitizes innerHTML', () => {
-    let interpolated = element(By.className('e2e-inner-html-interpolated'));
+    const interpolated = element(By.className('e2e-inner-html-interpolated'));
     expect(interpolated.getText())
         .toContain('Template <script>alert("0wned")</script> <b>Syntax</b>');
-    let bound = element(By.className('e2e-inner-html-bound'));
+    const bound = element(By.className('e2e-inner-html-bound'));
     expect(bound.getText()).toContain('Template Syntax');
-    let bold = element(By.css('.e2e-inner-html-bound b'));
+    const bold = element(By.css('.e2e-inner-html-bound b'));
     expect(bold.getText()).toContain('Syntax');
   });
 
   it('escapes untrusted URLs', () => {
-    let untrustedUrl = element(By.className('e2e-dangerous-url'));
+    const untrustedUrl = element(By.className('e2e-dangerous-url'));
     expect(untrustedUrl.getAttribute('href')).toMatch(/^unsafe:javascript/);
   });
 
   it('binds trusted URLs', () => {
-    let trustedUrl = element(By.className('e2e-trusted-url'));
+    const trustedUrl = element(By.className('e2e-trusted-url'));
     expect(trustedUrl.getAttribute('href')).toMatch(/^javascript:alert/);
   });
 
   it('escapes untrusted resource URLs', () => {
-    let iframe = element(By.className('e2e-iframe-untrusted-src'));
+    const iframe = element(By.className('e2e-iframe-untrusted-src'));
     expect(iframe.getAttribute('src')).toBe('');
   });
 
   it('binds trusted resource URLs', () => {
-    let iframe = element(By.className('e2e-iframe-trusted-src'));
+    const iframe = element(By.className('e2e-iframe-trusted-src'));
     expect(iframe.getAttribute('src')).toMatch(/^https:\/\/www.youtube.com\//);
   });
 });

aio/content/examples/service-worker-getting-started/e2e/src/app.e2e-spec.ts

@@ -15,7 +15,7 @@ describe('sw-example App', () => {
   });
 
   it('should display the Angular logo', () => {
-    let logo = element(by.css('img'));
+    const logo = element(by.css('img'));
     page.navigateTo();
     expect(logo.isPresent()).toBe(true);
   });

aio/content/examples/set-document-title/e2e/src/app.e2e-spec.ts

@@ -6,7 +6,7 @@ describe('Set Document Title', () => {
 
   it('should set the document title', () => {
 
-    let titles = [
+    const titles = [
       'Good morning!',
       'Good afternoon!',
       'Good evening!'

aio/content/examples/setup/e2e/src/app.e2e-spec.ts

@@ -2,7 +2,7 @@ import { browser, element, by } from 'protractor';
 
 describe('QuickStart E2E Tests', () => {
 
-  let expectedMsg = 'Hello Angular';
+  const expectedMsg = 'Hello Angular';
 
   beforeEach(() => {
     browser.get('');

aio/content/examples/styleguide/e2e/src/app.e2e-spec.ts

@@ -4,7 +4,7 @@ describe('Style Guide', () => {
   it('01-01', () => {
     browser.get('#/01-01');
 
-    let pre = element(by.tagName('toh-heroes > pre'));
+    const pre = element(by.tagName('toh-heroes > pre'));
     expect(pre.getText()).toContain('Bombasto');
     expect(pre.getText()).toContain('Tornado');
     expect(pre.getText()).toContain('Magneta');
@@ -13,8 +13,8 @@ describe('Style Guide', () => {
   it('02-07', () => {
     browser.get('#/02-07');
 
-    let hero = element(by.tagName('toh-hero > div'));
+    const hero = element(by.tagName('toh-hero > div'));
-    let users = element(by.tagName('admin-users > div'));
+    const users = element(by.tagName('admin-users > div'));
 
     expect(hero.getText()).toBe('hero component');
     expect(users.getText()).toBe('users component');
@@ -23,77 +23,77 @@ describe('Style Guide', () => {
   it('02-08', () => {
     browser.get('#/02-08');
 
-    let input = element(by.tagName('input[tohvalidate]'));
+    const input = element(by.tagName('input[tohvalidate]'));
     expect(input.isPresent()).toBe(true);
   });
 
   it('04-10', () => {
     browser.get('#/04-10');
 
-    let div = element(by.tagName('sg-app > toh-heroes > div'));
+    const div = element(by.tagName('sg-app > toh-heroes > div'));
     expect(div.getText()).toBe('This is heroes component');
   });
 
   it('05-02', () => {
     browser.get('#/05-02');
 
-    let button = element(by.tagName('sg-app > toh-hero-button > button'));
+    const button = element(by.tagName('sg-app > toh-hero-button > button'));
     expect(button.getText()).toBe('Hero button');
   });
 
   it('05-03', () => {
     browser.get('#/05-03');
 
-    let button = element(by.tagName('sg-app > toh-hero-button > button'));
+    const button = element(by.tagName('sg-app > toh-hero-button > button'));
     expect(button.getText()).toBe('Hero button');
   });
 
   it('05-04', () => {
     browser.get('#/05-04');
 
-    let h2 = element(by.tagName('sg-app > toh-heroes > div > h2'));
+    const h2 = element(by.tagName('sg-app > toh-heroes > div > h2'));
     expect(h2.getText()).toBe('My Heroes');
   });
 
   it('05-12', () => {
     browser.get('#/05-12');
 
-    let button = element(by.tagName('sg-app > toh-hero-button > button'));
+    const button = element(by.tagName('sg-app > toh-hero-button > button'));
     expect(button.getText()).toBe('OK');
   });
 
   it('05-13', () => {
     browser.get('#/05-13');
 
-    let button = element(by.tagName('sg-app > toh-hero-button > button'));
+    const button = element(by.tagName('sg-app > toh-hero-button > button'));
     expect(button.getText()).toBe('OK');
   });
 
   it('05-14', () => {
     browser.get('#/05-14');
 
-    let toast = element(by.tagName('sg-app > toh-toast'));
+    const toast = element(by.tagName('sg-app > toh-toast'));
     expect(toast.getText()).toBe('...');
   });
 
   it('05-15', () => {
     browser.get('#/05-15');
 
-    let heroList = element(by.tagName('sg-app > toh-hero-list'));
+    const heroList = element(by.tagName('sg-app > toh-hero-list'));
     expect(heroList.getText()).toBe('...');
   });
 
   it('05-16', () => {
     browser.get('#/05-16');
 
-    let hero = element(by.tagName('sg-app > toh-hero'));
+    const hero = element(by.tagName('sg-app > toh-hero'));
     expect(hero.getText()).toBe('...');
   });
 
   it('05-17', () => {
     browser.get('#/05-17');
 
-    let section = element(by.tagName('sg-app > toh-hero-list > section'));
+    const section = element(by.tagName('sg-app > toh-hero-list > section'));
     expect(section.getText()).toContain('Our list of heroes');
     expect(section.getText()).toContain('Total powers');
     expect(section.getText()).toContain('Average power');
@@ -102,14 +102,14 @@ describe('Style Guide', () => {
   it('06-01', () => {
     browser.get('#/06-01');
 
-    let div = element(by.tagName('sg-app > div[tohhighlight]'));
+    const div = element(by.tagName('sg-app > div[tohhighlight]'));
     expect(div.getText()).toBe('Bombasta');
   });
 
   it('06-03', () => {
     browser.get('#/06-03');
 
-    let input = element(by.tagName('input[tohvalidator]'));
+    const input = element(by.tagName('input[tohvalidator]'));
     expect(input.isPresent()).toBe(true);
   });
 
@@ -117,7 +117,7 @@ describe('Style Guide', () => {
   xit('07-01', () => {
     browser.get('#/07-01');
 
-    let lis = element.all(by.tagName('sg-app > ul > li'));
+    const lis = element.all(by.tagName('sg-app > ul > li'));
     expect(lis.get(0).getText()).toBe('Windstorm');
     expect(lis.get(1).getText()).toBe('Bombasto');
     expect(lis.get(2).getText()).toBe('Magneta');
@@ -127,21 +127,21 @@ describe('Style Guide', () => {
   it('07-03', () => {
     browser.get('#/07-03');
 
-    let pre = element(by.tagName('toh-heroes > pre'));
+    const pre = element(by.tagName('toh-heroes > pre'));
     expect(pre.getText()).toContain('[]');
   });
 
   it('07-04', () => {
     browser.get('#/07-04');
 
-    let pre = element(by.tagName('toh-app > pre'));
+    const pre = element(by.tagName('toh-app > pre'));
     expect(pre.getText()).toContain('[]');
   });
 
   it('09-01', () => {
     browser.get('#/09-01');
 
-    let button = element(by.tagName('sg-app > toh-hero-button > button'));
+    const button = element(by.tagName('sg-app > toh-hero-button > button'));
     expect(button.getText()).toBe('OK');
   });
 });

aio/content/examples/styleguide/src/04-10/app/shared/filter-text/filter-text.service.ts

@@ -11,9 +11,9 @@ export class FilterTextService {
     let filteredList: any[];
     if (data && props && originalList) {
       data = data.toLowerCase();
-      let filtered = originalList.filter(item => {
+      const filtered = originalList.filter(item => {
         let match = false;
-        for (let prop of props) {
+        for (const prop of props) {
           if (item[prop].toString().toLowerCase().indexOf(data) > -1) {
             match = true;
             break;

aio/content/examples/styleguide/src/05-15/app/heroes/shared/hero.service.ts

@@ -8,7 +8,7 @@ import { Hero } from './hero.model';
 @Injectable()
 export class HeroService {
   getHeroes() {
-    let heroes: Hero[] = [];
+    const heroes: Hero[] = [];
     return of(heroes);
   }
 }

aio/content/examples/styleguide/src/07-03/app/heroes/shared/hero.service.ts

@@ -10,7 +10,7 @@ import { Hero } from './hero.model';
 })
 export class HeroService {
   getHeroes() {
-    let heroes: Hero[] = [];
+    const heroes: Hero[] = [];
     return of(heroes);
   }
 }

aio/content/examples/styleguide/src/07-04/app/heroes/shared/hero.service.ts

@@ -8,7 +8,7 @@ import { Hero } from './hero.model';
 @Injectable()
 export class HeroService {
   getHeroes() {
-    let heroes: Hero[] = [];
+    const heroes: Hero[] = [];
     return of(heroes);
   }
 }

aio/content/examples/styleguide/src/app/hero-data.ts

@@ -1,6 +1,6 @@
 export class HeroData {
   createDb() {
-    let heroes = [
+    const heroes = [
       { id: 1, name: 'Windstorm' },
       { id: 2, name: 'Bombasto' },
       { id: 3, name: 'Magneta' },

aio/content/examples/template-expression-operators/e2e/src/app.e2e-spec.ts

@@ -8,22 +8,22 @@ describe('Template Expression Operators', () => {
   });
 
   it('should have title Inputs and Outputs', () => {
-    let title = element.all(by.css('h1')).get(0);
+    const title = element.all(by.css('h1')).get(0);
     expect(title.getText()).toEqual('Template Expression Operators');
   });
 
   it('should display json data', () => {
-    let jsonDate = element.all(by.css('p')).get(4);
+    const jsonDate = element.all(by.css('p')).get(4);
     expect(jsonDate.getText()).toContain('1980');
   });
 
   it('should display $98', () => {
-    let jsonDate = element.all(by.css('p')).get(5);
+    const jsonDate = element.all(by.css('p')).get(5);
     expect(jsonDate.getText()).toContain('$98.00');
   });
 
   it('should display Telephone', () => {
-    let jsonDate = element.all(by.css('p')).get(6);
+    const jsonDate = element.all(by.css('p')).get(6);
     expect(jsonDate.getText()).toContain('Telephone');
   });
 

aio/content/examples/template-reference-variables/e2e/src/app.e2e-spec.ts

@@ -21,8 +21,8 @@ describe('Template-reference-variables-example', () => {
   });
 
   it('should log a Calling 123 ... message', async () => {
-    let callButton = element.all(by.css('button')).get(0);
+    const callButton = element.all(by.css('button')).get(0);
-    let phoneInput = element.all(by.css('input')).get(0);
+    const phoneInput = element.all(by.css('input')).get(0);
     await phoneInput.sendKeys('123');
     await callButton.click();
     const contents = 'Calling 123 ...';
@@ -30,8 +30,8 @@ describe('Template-reference-variables-example', () => {
   });
 
   it('should log a Faxing 123 ... message', async () => {
-    let faxButton = element.all(by.css('button')).get(1);
+    const faxButton = element.all(by.css('button')).get(1);
-    let faxInput = element.all(by.css('input')).get(1);
+    const faxInput = element.all(by.css('input')).get(1);
     await faxInput.sendKeys('123');
     await faxButton.click();
     const contents = 'Faxing 123 ...';
@@ -39,13 +39,13 @@ describe('Template-reference-variables-example', () => {
   });
 
   it('should display a disabled button', () => {
-    let disabledButton = element.all(by.css('button')).get(2);
+    const disabledButton = element.all(by.css('button')).get(2);
     expect(disabledButton.isEnabled()).toBe(false);
   });
 
   it('should submit form', async () => {
-    let submitButton = element.all(by.css('button')).get(3);
+    const submitButton = element.all(by.css('button')).get(3);
-    let nameInput = element.all(by.css('input')).get(2);
+    const nameInput = element.all(by.css('input')).get(2);
     await nameInput.sendKeys('123');
     await submitButton.click();
     expect(element.all(by.css('div > p')).get(2).getText()).toEqual('Submitted. Form value is {"name":"123"}');

aio/content/examples/testing/e2e/src/app.e2e-spec.ts

@@ -6,7 +6,7 @@ describe('Testing Example', () => {
   beforeAll(() => browser.get(''));
 
   function getPageElts() {
-    let navElts = element.all(by.css('app-root nav a'));
+    const navElts = element.all(by.css('app-root nav a'));
 
     return {
       navElts,
@@ -20,13 +20,13 @@ describe('Testing Example', () => {
   });
 
   it(`has views ${expectedViewNames}`, async () => {
-    let viewNames = getPageElts().navElts.map(async (el: ElementFinder) => await el.getText());
+    const viewNames = getPageElts().navElts.map(async (el: ElementFinder) => await el.getText());
 
     expect(viewNames).toEqual(expectedViewNames);
   });
 
   it('has dashboard as the active view', () => {
-    let page = getPageElts();
+    const page = getPageElts();
 
     expect(page.appDashboard.isPresent()).toBeTruthy();
   });

aio/content/examples/testing/src/app/dashboard/dashboard.component.ts

@@ -28,13 +28,13 @@ export class DashboardComponent implements OnInit {
 
   // #docregion goto-detail
   gotoDetail(hero: Hero) {
-    let url = `/heroes/${hero.id}`;
+    const url = `/heroes/${hero.id}`;
     this.router.navigateByUrl(url);
   }
   // #enddocregion goto-detail
 
   get title() {
-    let cnt = this.heroes.length;
+    const cnt = this.heroes.length;
     return cnt === 0 ? 'No Heroes' :
       cnt === 1 ? 'Top Hero' :  `Top ${cnt} Heroes`;
   }

aio/content/examples/testing/src/app/demo/demo.ts

@@ -310,11 +310,11 @@ export class MyIfChildComponent implements OnInit, OnChanges, OnDestroy {
   }
 
   ngOnChanges(changes: {[propertyName: string]: SimpleChange}) {
-    for (let propName in changes) {
+    for (const propName in changes) {
       this.ngOnChangesCounter += 1;
-      let prop = changes[propName];
+      const prop = changes[propName];
-      let cur  = JSON.stringify(prop.currentValue);
+      const cur  = JSON.stringify(prop.currentValue);
-      let prev = JSON.stringify(prop.previousValue);
+      const prev = JSON.stringify(prop.previousValue);
       this.changeLog.push(`${propName}: currentValue = ${cur}, previousValue = ${prev}`);
     }
   }

aio/content/examples/testing/src/app/model/testing/http-client.spec.ts

@@ -89,7 +89,7 @@ describe('HttpClient testing', () => {
   });
 
   it('can test multiple requests', () => {
-    let testData: Data[] = [
+    const testData: Data[] = [
       { name: 'bob' }, { name: 'carol' },
       { name: 'ted' }, { name: 'alice' }
     ];

aio/content/examples/testing/src/app/shared/title-case.pipe.spec.ts

@@ -5,7 +5,7 @@ import { TitleCasePipe } from './title-case.pipe';
 // #docregion excerpt, mini-excerpt
 describe('TitleCasePipe', () => {
   // This pipe is a pure, stateless function so no need for BeforeEach
-  let pipe = new TitleCasePipe();
+  const pipe = new TitleCasePipe();
 
   it('transforms "abc" to "Abc"', () => {
     expect(pipe.transform('abc')).toBe('Abc');

aio/content/examples/testing/src/testing/index.ts

@@ -21,7 +21,7 @@ export function advance(f: ComponentFixture<any>): void {
  * Although officially deprecated, some browsers (phantom) don't accept the preferred "new Event(eventName)"
  */
 export function newEvent(eventName: string, bubbles = false, cancelable = false) {
-  let evt = document.createEvent('CustomEvent');  // MUST be 'CustomEvent'
+  const evt = document.createEvent('CustomEvent');  // MUST be 'CustomEvent'
   evt.initCustomEvent(eventName, bubbles, cancelable, null);
   return evt;
 }

aio/content/examples/toh-pt0/e2e/src/app.e2e-spec.ts

@@ -4,7 +4,7 @@ describe('Tour of Heroes', () => {
   beforeEach(() => browser.get('/'));
 
   it('should display "Tour of Heroes"', () => {
-    let title = element(by.css('app-root h1')).getText();
+    const title = element(by.css('app-root h1')).getText();
     expect(title).toEqual('Tour of Heroes');
   });
 });

aio/content/examples/toh-pt1/e2e/src/app.e2e-spec.ts

@@ -12,9 +12,9 @@ class Hero {
   // Get hero id and name from the given detail element.
   static async fromDetail(detail: ElementFinder): Promise<Hero> {
     // Get hero id from the first <div>
-    let id = await detail.all(by.css('div')).first().getText();
+    const id = await detail.all(by.css('div')).first().getText();
     // Get name from the h2
-    let name = await detail.element(by.css('h2')).getText();
+    const name = await detail.element(by.css('h2')).getText();
     return {
       id: +id.substr(id.indexOf(' ') + 1),
       name: name.substr(0, name.lastIndexOf(' '))
@@ -24,7 +24,7 @@ class Hero {
 
 const nameSuffix = 'X';
 function addToHeroName(text: string): promise.Promise<void> {
-  let input = element(by.css('input'));
+  const input = element(by.css('input'));
   return input.sendKeys(text);
 }
 
@@ -39,22 +39,22 @@ describe('Tutorial part 1', () => {
   });
 
   it(`has h1 '${expectedH1}'`, () => {
-    let hText = element(by.css('h1')).getText();
+    const hText = element(by.css('h1')).getText();
     expect(hText).toEqual(expectedH1, 'h1');
   });
 
   it(`shows initial hero details`, async () => {
-    let page = getPageElts();
+    const page = getPageElts();
-    let hero = await Hero.fromDetail(page.heroDetail);
+    const hero = await Hero.fromDetail(page.heroDetail);
     expect(hero.id).toEqual(expectedHero.id);
     expect(hero.name).toEqual(expectedHero.name.toUpperCase());
   });
 
   it(`shows updated hero name`, async () => {
     addToHeroName(nameSuffix);
-    let page = getPageElts();
+    const page = getPageElts();
-    let hero = await Hero.fromDetail(page.heroDetail);
+    const hero = await Hero.fromDetail(page.heroDetail);
-    let newName = expectedHero.name + nameSuffix;
+    const newName = expectedHero.name + nameSuffix;
     expect(hero.id).toEqual(expectedHero.id);
     expect(hero.name).toEqual(newName.toUpperCase());
   });

aio/content/examples/toh-pt2/e2e/src/app.e2e-spec.ts

@@ -24,9 +24,9 @@ class Hero {
     // Get hero id and name from the given detail element.
     static async fromDetail(detail: ElementFinder): Promise<Hero> {
         // Get hero id from the first <div>
-        let id = await detail.all(by.css('div')).first().getText();
+        const id = await detail.all(by.css('div')).first().getText();
         // Get name from the h2
-        let name = await detail.element(by.css('h2')).getText();
+        const name = await detail.element(by.css('h2')).getText();
         return {
             id: +id.substr(id.indexOf(' ') + 1),
             name: name.substr(0, name.lastIndexOf(' '))
@@ -55,12 +55,12 @@ function initialPageTests() {
   });
 
   it('has the right number of heroes', () => {
-    let page = getPageElts();
+    const page = getPageElts();
     expect(page.heroes.count()).toEqual(10);
   });
 
   it('has no selected hero and no hero details', () => {
-    let page = getPageElts();
+    const page = getPageElts();
     expect(page.selected.isPresent()).toBeFalsy('selected hero');
     expect(page.heroDetail.isPresent()).toBeFalsy('no hero detail');
   });
@@ -68,20 +68,20 @@ function initialPageTests() {
 
 function selectHeroTests() {
   it(`selects ${targetHero.name} from hero list`, () => {
-    let hero = element(by.cssContainingText('li span.badge', targetHero.id.toString()));
+    const hero = element(by.cssContainingText('li span.badge', targetHero.id.toString()));
     hero.click();
     // Nothing specific to expect other than lack of exceptions.
   });
 
   it(`has selected ${targetHero.name}`, () => {
-    let page = getPageElts();
+    const page = getPageElts();
-    let expectedText = `${targetHero.id} ${targetHero.name}`;
+    const expectedText = `${targetHero.id} ${targetHero.name}`;
     expect(page.selected.getText()).toBe(expectedText);
   });
 
   it('shows selected hero details', async () => {
-    let page = getPageElts();
+    const page = getPageElts();
-    let hero = await Hero.fromDetail(page.heroDetail);
+    const hero = await Hero.fromDetail(page.heroDetail);
     expect(hero.id).toEqual(targetHero.id);
     expect(hero.name).toEqual(targetHero.name.toUpperCase());
   });
@@ -94,17 +94,17 @@ function updateHeroTests() {
   });
 
   it(`shows updated hero name in details`, async () => {
-    let page = getPageElts();
+    const page = getPageElts();
-    let hero = await Hero.fromDetail(page.heroDetail);
+    const hero = await Hero.fromDetail(page.heroDetail);
-    let newName = targetHero.name + nameSuffix;
+    const newName = targetHero.name + nameSuffix;
     expect(hero.id).toEqual(targetHero.id);
     expect(hero.name).toEqual(newName.toUpperCase());
   });
 
   it(`shows updated hero name in list`, async () => {
-    let page = getPageElts();
+    const page = getPageElts();
-    let hero = Hero.fromString(await page.selected.getText());
+    const hero = Hero.fromString(await page.selected.getText());
-    let newName = targetHero.name + nameSuffix;
+    const newName = targetHero.name + nameSuffix;
     expect(hero.id).toEqual(targetHero.id);
     expect(hero.name).toEqual(newName);
   });
@@ -112,13 +112,13 @@ function updateHeroTests() {
 }
 
 function addToHeroName(text: string): promise.Promise<void> {
-  let input = element(by.css('input'));
+  const input = element(by.css('input'));
   return input.sendKeys(text);
 }
 
 function expectHeading(hLevel: number, expectedText: string): void {
-    let hTag = `h${hLevel}`;
+    const hTag = `h${hLevel}`;
-    let hText = element(by.css(hTag)).getText();
+    const hText = element(by.css(hTag)).getText();
     expect(hText).toEqual(expectedText, hTag);
 }
 

aio/content/examples/toh-pt3/e2e/src/app.e2e-spec.ts

@@ -24,9 +24,9 @@ class Hero {
     // Get hero id and name from the given detail element.
     static async fromDetail(detail: ElementFinder): Promise<Hero> {
         // Get hero id from the first <div>
-        let id = await detail.all(by.css('div')).first().getText();
+        const id = await detail.all(by.css('div')).first().getText();
         // Get name from the h2
-        let name = await detail.element(by.css('h2')).getText();
+        const name = await detail.element(by.css('h2')).getText();
         return {
             id: +id.substr(id.indexOf(' ') + 1),
             name: name.substr(0, name.lastIndexOf(' '))
@@ -55,12 +55,12 @@ function initialPageTests() {
   });
 
   it('has the right number of heroes', () => {
-    let page = getPageElts();
+    const page = getPageElts();
     expect(page.heroes.count()).toEqual(10);
   });
 
   it('has no selected hero and no hero details', () => {
-    let page = getPageElts();
+    const page = getPageElts();
     expect(page.selected.isPresent()).toBeFalsy('selected hero');
     expect(page.heroDetail.isPresent()).toBeFalsy('no hero detail');
   });
@@ -68,20 +68,20 @@ function initialPageTests() {
 
 function selectHeroTests() {
   it(`selects ${targetHero.name} from hero list`, () => {
-    let hero = element(by.cssContainingText('li span.badge', targetHero.id.toString()));
+    const hero = element(by.cssContainingText('li span.badge', targetHero.id.toString()));
     hero.click();
     // Nothing specific to expect other than lack of exceptions.
   });
 
   it(`has selected ${targetHero.name}`, () => {
-    let page = getPageElts();
+    const page = getPageElts();
-    let expectedText = `${targetHero.id} ${targetHero.name}`;
+    const expectedText = `${targetHero.id} ${targetHero.name}`;
     expect(page.selected.getText()).toBe(expectedText);
   });
 
   it('shows selected hero details', async () => {
-    let page = getPageElts();
+    const page = getPageElts();
-    let hero = await Hero.fromDetail(page.heroDetail);
+    const hero = await Hero.fromDetail(page.heroDetail);
     expect(hero.id).toEqual(targetHero.id);
     expect(hero.name).toEqual(targetHero.name.toUpperCase());
   });
@@ -94,17 +94,17 @@ function updateHeroTests() {
   });
 
   it(`shows updated hero name in details`, async () => {
-    let page = getPageElts();
+    const page = getPageElts();
-    let hero = await Hero.fromDetail(page.heroDetail);
+    const hero = await Hero.fromDetail(page.heroDetail);
-    let newName = targetHero.name + nameSuffix;
+    const newName = targetHero.name + nameSuffix;
     expect(hero.id).toEqual(targetHero.id);
     expect(hero.name).toEqual(newName.toUpperCase());
   });
 
   it(`shows updated hero name in list`, async () => {
-    let page = getPageElts();
+    const page = getPageElts();
-    let hero = Hero.fromString(await page.selected.getText());
+    const hero = Hero.fromString(await page.selected.getText());
-    let newName = targetHero.name + nameSuffix;
+    const newName = targetHero.name + nameSuffix;
     expect(hero.id).toEqual(targetHero.id);
     expect(hero.name).toEqual(newName);
   });
@@ -112,13 +112,13 @@ function updateHeroTests() {
 }
 
 function addToHeroName(text: string): promise.Promise<void> {
-  let input = element(by.css('input'));
+  const input = element(by.css('input'));
   return input.sendKeys(text);
 }
 
 function expectHeading(hLevel: number, expectedText: string): void {
-    let hTag = `h${hLevel}`;
+    const hTag = `h${hLevel}`;
-    let hText = element(by.css(hTag)).getText();
+    const hText = element(by.css(hTag)).getText();
     expect(hText).toEqual(expectedText, hTag);
 }
 

aio/content/examples/toh-pt4/e2e/src/app.e2e-spec.ts

@@ -24,9 +24,9 @@ class Hero {
     // Get hero id and name from the given detail element.
     static async fromDetail(detail: ElementFinder): Promise<Hero> {
         // Get hero id from the first <div>
-        let id = await detail.all(by.css('div')).first().getText();
+        const id = await detail.all(by.css('div')).first().getText();
         // Get name from the h2
-        let name = await detail.element(by.css('h2')).getText();
+        const name = await detail.element(by.css('h2')).getText();
         return {
             id: +id.substr(id.indexOf(' ') + 1),
             name: name.substr(0, name.lastIndexOf(' '))
@@ -55,12 +55,12 @@ function initialPageTests() {
   });
 
   it('has the right number of heroes', () => {
-    let page = getPageElts();
+    const page = getPageElts();
     expect(page.heroes.count()).toEqual(10);
   });
 
   it('has no selected hero and no hero details', () => {
-    let page = getPageElts();
+    const page = getPageElts();
     expect(page.selected.isPresent()).toBeFalsy('selected hero');
     expect(page.heroDetail.isPresent()).toBeFalsy('no hero detail');
   });
@@ -68,21 +68,21 @@ function initialPageTests() {
 
 function selectHeroTests() {
   it(`selects ${targetHero.name} from hero list`, () => {
-    let hero = element(by.cssContainingText('li span.badge', targetHero.id.toString()));
+    const hero = element(by.cssContainingText('li span.badge', targetHero.id.toString()));
     hero.click();
     // Nothing specific to expect other than lack of exceptions.
   });
 
   it(`has selected ${targetHero.name}`, () => {
-    let page = getPageElts();
+    const page = getPageElts();
-    let expectedText = `${targetHero.id} ${targetHero.name}`;
+    const expectedText = `${targetHero.id} ${targetHero.name}`;
     expect(page.selected.getText()).toBe(expectedText);
   });
 
   it('shows selected hero details', async () => {
-    let page = getPageElts();
+    const page = getPageElts();
-    let message = getMessage();
+    const message = getMessage();
-    let hero = await Hero.fromDetail(page.heroDetail);
+    const hero = await Hero.fromDetail(page.heroDetail);
     expect(hero.id).toEqual(targetHero.id);
     expect(hero.name).toEqual(targetHero.name.toUpperCase());
     // Message text contain id number matches the hero.id number
@@ -98,17 +98,17 @@ function updateHeroTests() {
   });
 
   it(`shows updated hero name in details`, async () => {
-    let page = getPageElts();
+    const page = getPageElts();
-    let hero = await Hero.fromDetail(page.heroDetail);
+    const hero = await Hero.fromDetail(page.heroDetail);
-    let newName = targetHero.name + nameSuffix;
+    const newName = targetHero.name + nameSuffix;
     expect(hero.id).toEqual(targetHero.id);
     expect(hero.name).toEqual(newName.toUpperCase());
   });
 
   it(`shows updated hero name in list`, async () => {
-    let page = getPageElts();
+    const page = getPageElts();
-    let hero = Hero.fromString(await page.selected.getText());
+    const hero = Hero.fromString(await page.selected.getText());
-    let newName = targetHero.name + nameSuffix;
+    const newName = targetHero.name + nameSuffix;
     expect(hero.id).toEqual(targetHero.id);
     expect(hero.name).toEqual(newName);
   });
@@ -116,13 +116,13 @@ function updateHeroTests() {
 }
 
 function addToHeroName(text: string): promise.Promise<void> {
-  let input = element(by.css('input'));
+  const input = element(by.css('input'));
   return input.sendKeys(text);
 }
 
 function expectHeading(hLevel: number, expectedText: string): void {
-    let hTag = `h${hLevel}`;
+    const hTag = `h${hLevel}`;
-    let hText = element(by.css(hTag)).getText();
+    const hText = element(by.css(hTag)).getText();
     expect(hText).toEqual(expectedText, hTag);
 }
 
@@ -135,7 +135,7 @@ function getPageElts() {
 }
 
 function getMessage() {
-  let hero = element(by.cssContainingText('li span.badge', targetHero.id.toString()));
+  const hero = element(by.cssContainingText('li span.badge', targetHero.id.toString()));
   hero.click();
   return element.all(by.css('app-root > app-messages > div > div')).get(1);
 }

aio/content/examples/toh-pt5/e2e/src/app.e2e-spec.ts

@@ -25,9 +25,9 @@ class Hero {
     // Get hero id and name from the given detail element.
     static async fromDetail(detail: ElementFinder): Promise<Hero> {
         // Get hero id from the first <div>
-        let id = await detail.all(by.css('div')).first().getText();
+        const id = await detail.all(by.css('div')).first().getText();
         // Get name from the h2
-        let name = await detail.element(by.css('h2')).getText();
+        const name = await detail.element(by.css('h2')).getText();
         return {
             id: +id.substr(id.indexOf(' ') + 1),
             name: name.substr(0, name.lastIndexOf(' '))
@@ -40,7 +40,7 @@ describe('Tutorial part 5', () => {
   beforeAll(() => browser.get(''));
 
   function getPageElts() {
-    let navElts = element.all(by.css('app-root nav a'));
+    const navElts = element.all(by.css('app-root nav a'));
 
     return {
       navElts,
@@ -68,12 +68,12 @@ describe('Tutorial part 5', () => {
 
     const expectedViewNames = ['Dashboard', 'Heroes'];
     it(`has views ${expectedViewNames}`, () => {
-      let viewNames = getPageElts().navElts.map((el: ElementFinder) => el.getText());
+      const viewNames = getPageElts().navElts.map((el: ElementFinder) => el.getText());
       expect(viewNames).toEqual(expectedViewNames);
     });
 
     it('has dashboard as the active view', () => {
-      let page = getPageElts();
+      const page = getPageElts();
       expect(page.appDashboard.isPresent()).toBeTruthy();
     });
 
@@ -84,7 +84,7 @@ describe('Tutorial part 5', () => {
     beforeAll(() => browser.get(''));
 
     it('has top heroes', () => {
-      let page = getPageElts();
+      const page = getPageElts();
       expect(page.topHeroes.count()).toEqual(4);
     });
 
@@ -94,7 +94,7 @@ describe('Tutorial part 5', () => {
 
     it(`saves and shows ${newHeroName} in Dashboard`, () => {
       element(by.buttonText('go back')).click();
-      let targetHeroElt = getPageElts().topHeroes.get(targetHeroDashboardIndex);
+      const targetHeroElt = getPageElts().topHeroes.get(targetHeroDashboardIndex);
       expect(targetHeroElt.getText()).toEqual(newHeroName);
     });
 
@@ -106,7 +106,7 @@ describe('Tutorial part 5', () => {
 
     it('can switch to Heroes view', () => {
       getPageElts().appHeroesHref.click();
-      let page = getPageElts();
+      const page = getPageElts();
       expect(page.appHeroes.isPresent()).toBeTruthy();
       expect(page.allHeroes.count()).toEqual(10, 'number of heroes');
     });
@@ -114,9 +114,9 @@ describe('Tutorial part 5', () => {
     it('can route to hero details', async () => {
       getHeroLiEltById(targetHero.id).click();
 
-      let page = getPageElts();
+      const page = getPageElts();
       expect(page.heroDetail.isPresent()).toBeTruthy('shows hero detail');
-      let hero = await Hero.fromDetail(page.heroDetail);
+      const hero = await Hero.fromDetail(page.heroDetail);
       expect(hero.id).toEqual(targetHero.id);
       expect(hero.name).toEqual(targetHero.name.toUpperCase());
     });
@@ -125,20 +125,20 @@ describe('Tutorial part 5', () => {
 
     it(`shows ${newHeroName} in Heroes list`, () => {
       element(by.buttonText('go back')).click();
-      let expectedText = `${targetHero.id} ${newHeroName}`;
+      const expectedText = `${targetHero.id} ${newHeroName}`;
       expect(getHeroLiEltById(targetHero.id).getText()).toEqual(expectedText);
     });
 
   });
 
   async function dashboardSelectTargetHero() {
-    let targetHeroElt = getPageElts().topHeroes.get(targetHeroDashboardIndex);
+    const targetHeroElt = getPageElts().topHeroes.get(targetHeroDashboardIndex);
     expect(targetHeroElt.getText()).toEqual(targetHero.name);
     targetHeroElt.click();
 
-    let page = getPageElts();
+    const page = getPageElts();
     expect(page.heroDetail.isPresent()).toBeTruthy('shows hero detail');
-    let hero = await Hero.fromDetail(page.heroDetail);
+    const hero = await Hero.fromDetail(page.heroDetail);
     expect(hero.id).toEqual(targetHero.id);
     expect(hero.name).toEqual(targetHero.name.toUpperCase());
   }
@@ -147,8 +147,8 @@ describe('Tutorial part 5', () => {
     // Assumes that the current view is the hero details view.
     addToHeroName(nameSuffix);
 
-    let page = getPageElts();
+    const page = getPageElts();
-    let hero = await Hero.fromDetail(page.heroDetail);
+    const hero = await Hero.fromDetail(page.heroDetail);
     expect(hero.id).toEqual(targetHero.id);
     expect(hero.name).toEqual(newHeroName.toUpperCase());
   }
@@ -156,17 +156,17 @@ describe('Tutorial part 5', () => {
 });
 
 function addToHeroName(text: string): promise.Promise<void> {
-  let input = element(by.css('input'));
+  const input = element(by.css('input'));
   return input.sendKeys(text);
 }
 
 function expectHeading(hLevel: number, expectedText: string): void {
-    let hTag = `h${hLevel}`;
+    const hTag = `h${hLevel}`;
-    let hText = element(by.css(hTag)).getText();
+    const hText = element(by.css(hTag)).getText();
     expect(hText).toEqual(expectedText, hTag);
 }
 
 function getHeroLiEltById(id: number) {
-  let spanForId = element(by.cssContainingText('li span.badge', id.toString()));
+  const spanForId = element(by.cssContainingText('li span.badge', id.toString()));
   return spanForId.element(by.xpath('..'));
 }

aio/content/examples/toh-pt6/e2e/src/app.e2e-spec.ts

@@ -24,17 +24,17 @@ class Hero {
 
   // Hero from hero list <li> element.
   static async fromLi(li: ElementFinder): Promise<Hero> {
-      let stringsFromA = await li.all(by.css('a')).getText();
+      const stringsFromA = await li.all(by.css('a')).getText();
-      let strings = stringsFromA[0].split(' ');
+      const strings = stringsFromA[0].split(' ');
       return { id: +strings[0], name: strings[1] };
   }
 
   // Hero id and name from the given detail element.
   static async fromDetail(detail: ElementFinder): Promise<Hero> {
     // Get hero id from the first <div>
-    let id = await detail.all(by.css('div')).first().getText();
+    const id = await detail.all(by.css('div')).first().getText();
     // Get name from the h2
-    let name = await detail.element(by.css('h2')).getText();
+    const name = await detail.element(by.css('h2')).getText();
     return {
         id: +id.substr(id.indexOf(' ') + 1),
         name: name.substr(0, name.lastIndexOf(' '))
@@ -47,7 +47,7 @@ describe('Tutorial part 6', () => {
   beforeAll(() => browser.get(''));
 
   function getPageElts() {
-    let navElts = element.all(by.css('app-root nav a'));
+    const navElts = element.all(by.css('app-root nav a'));
 
     return {
       navElts,
@@ -80,12 +80,12 @@ describe('Tutorial part 6', () => {
 
     const expectedViewNames = ['Dashboard', 'Heroes'];
     it(`has views ${expectedViewNames}`, () => {
-      let viewNames = getPageElts().navElts.map((el: ElementFinder) => el.getText());
+      const viewNames = getPageElts().navElts.map((el: ElementFinder) => el.getText());
       expect(viewNames).toEqual(expectedViewNames);
     });
 
     it('has dashboard as the active view', () => {
-      let page = getPageElts();
+      const page = getPageElts();
       expect(page.appDashboard.isPresent()).toBeTruthy();
     });
 
@@ -96,7 +96,7 @@ describe('Tutorial part 6', () => {
     beforeAll(() => browser.get(''));
 
     it('has top heroes', () => {
-      let page = getPageElts();
+      const page = getPageElts();
       expect(page.topHeroes.count()).toEqual(4);
     });
 
@@ -108,7 +108,7 @@ describe('Tutorial part 6', () => {
       element(by.buttonText('go back')).click();
       browser.waitForAngular(); // seems necessary to gets tests to pass for toh-pt6
 
-      let targetHeroElt = getPageElts().topHeroes.get(targetHeroDashboardIndex);
+      const targetHeroElt = getPageElts().topHeroes.get(targetHeroDashboardIndex);
       expect(targetHeroElt.getText()).toEqual(targetHero.name);
     });
 
@@ -120,7 +120,7 @@ describe('Tutorial part 6', () => {
       element(by.buttonText('save')).click();
       browser.waitForAngular(); // seems necessary to gets tests to pass for toh-pt6
 
-      let targetHeroElt = getPageElts().topHeroes.get(targetHeroDashboardIndex);
+      const targetHeroElt = getPageElts().topHeroes.get(targetHeroDashboardIndex);
       expect(targetHeroElt.getText()).toEqual(newHeroName);
     });
 
@@ -132,7 +132,7 @@ describe('Tutorial part 6', () => {
 
     it('can switch to Heroes view', () => {
       getPageElts().appHeroesHref.click();
-      let page = getPageElts();
+      const page = getPageElts();
       expect(page.appHeroes.isPresent()).toBeTruthy();
       expect(page.allHeroes.count()).toEqual(10, 'number of heroes');
     });
@@ -140,9 +140,9 @@ describe('Tutorial part 6', () => {
     it('can route to hero details', async () => {
       getHeroLiEltById(targetHero.id).click();
 
-      let page = getPageElts();
+      const page = getPageElts();
       expect(page.heroDetail.isPresent()).toBeTruthy('shows hero detail');
-      let hero = await Hero.fromDetail(page.heroDetail);
+      const hero = await Hero.fromDetail(page.heroDetail);
       expect(hero.id).toEqual(targetHero.id);
       expect(hero.name).toEqual(targetHero.name.toUpperCase());
     });
@@ -152,7 +152,7 @@ describe('Tutorial part 6', () => {
     it(`shows ${newHeroName} in Heroes list`, () => {
       element(by.buttonText('save')).click();
       browser.waitForAngular();
-      let expectedText = `${targetHero.id} ${newHeroName}`;
+      const expectedText = `${targetHero.id} ${newHeroName}`;
       expect(getHeroAEltById(targetHero.id).getText()).toEqual(expectedText);
     });
 
@@ -179,8 +179,8 @@ describe('Tutorial part 6', () => {
       element(by.css('input')).sendKeys(addedHeroName);
       element(by.buttonText('add')).click();
 
-      let page = getPageElts();
+      const page = getPageElts();
-      let heroesAfter = await toHeroArray(page.allHeroes);
+      const heroesAfter = await toHeroArray(page.allHeroes);
       expect(heroesAfter.length).toEqual(numHeroes + 1, 'number of heroes');
 
       expect(heroesAfter.slice(0, numHeroes)).toEqual(heroesBefore, 'Old heroes are still there');
@@ -233,34 +233,34 @@ describe('Tutorial part 6', () => {
     it(`continues search with 'e' and gets ${targetHero.name}`, async () => {
       getPageElts().searchBox.sendKeys('n');
       browser.sleep(1000);
-      let page = getPageElts();
+      const page = getPageElts();
       expect(page.searchResults.count()).toBe(1);
-      let hero = page.searchResults.get(0);
+      const hero = page.searchResults.get(0);
       expect(hero.getText()).toEqual(targetHero.name);
     });
 
     it(`navigates to ${targetHero.name} details view`, async () => {
-      let hero = getPageElts().searchResults.get(0);
+      const hero = getPageElts().searchResults.get(0);
       expect(hero.getText()).toEqual(targetHero.name);
       hero.click();
 
-      let page = getPageElts();
+      const page = getPageElts();
       expect(page.heroDetail.isPresent()).toBeTruthy('shows hero detail');
-      let hero2 = await Hero.fromDetail(page.heroDetail);
+      const hero2 = await Hero.fromDetail(page.heroDetail);
       expect(hero2.id).toEqual(targetHero.id);
       expect(hero2.name).toEqual(targetHero.name.toUpperCase());
     });
   });
 
   async function dashboardSelectTargetHero() {
-    let targetHeroElt = getPageElts().topHeroes.get(targetHeroDashboardIndex);
+    const targetHeroElt = getPageElts().topHeroes.get(targetHeroDashboardIndex);
     expect(targetHeroElt.getText()).toEqual(targetHero.name);
     targetHeroElt.click();
     browser.waitForAngular(); // seems necessary to gets tests to pass for toh-pt6
 
-    let page = getPageElts();
+    const page = getPageElts();
     expect(page.heroDetail.isPresent()).toBeTruthy('shows hero detail');
-    let hero = await Hero.fromDetail(page.heroDetail);
+    const hero = await Hero.fromDetail(page.heroDetail);
     expect(hero.id).toEqual(targetHero.id);
     expect(hero.name).toEqual(targetHero.name.toUpperCase());
   }
@@ -269,8 +269,8 @@ describe('Tutorial part 6', () => {
     // Assumes that the current view is the hero details view.
     addToHeroName(nameSuffix);
 
-    let page = getPageElts();
+    const page = getPageElts();
-    let hero = await Hero.fromDetail(page.heroDetail);
+    const hero = await Hero.fromDetail(page.heroDetail);
     expect(hero.id).toEqual(targetHero.id);
     expect(hero.name).toEqual(newHeroName.toUpperCase());
   }
@@ -278,28 +278,28 @@ describe('Tutorial part 6', () => {
 });
 
 function addToHeroName(text: string): promise.Promise<void> {
-  let input = element(by.css('input'));
+  const input = element(by.css('input'));
   return input.sendKeys(text);
 }
 
 function expectHeading(hLevel: number, expectedText: string): void {
-    let hTag = `h${hLevel}`;
+    const hTag = `h${hLevel}`;
-    let hText = element(by.css(hTag)).getText();
+    const hText = element(by.css(hTag)).getText();
     expect(hText).toEqual(expectedText, hTag);
 }
 
 function getHeroAEltById(id: number): ElementFinder {
-  let spanForId = element(by.cssContainingText('li span.badge', id.toString()));
+  const spanForId = element(by.cssContainingText('li span.badge', id.toString()));
   return spanForId.element(by.xpath('..'));
 }
 
 function getHeroLiEltById(id: number): ElementFinder {
-  let spanForId = element(by.cssContainingText('li span.badge', id.toString()));
+  const spanForId = element(by.cssContainingText('li span.badge', id.toString()));
   return spanForId.element(by.xpath('../..'));
 }
 
 async function toHeroArray(allHeroes: ElementArrayFinder): Promise<Hero[]> {
-  let promisedHeroes = await allHeroes.map(Hero.fromLi);
+  const promisedHeroes = await allHeroes.map(Hero.fromLi);
   // The cast is necessary to get around issuing with the signature of Promise.all()
   return Promise.all(promisedHeroes) as Promise<any>;
 }

aio/content/examples/two-way-binding/e2e/src/app.e2e-spec.ts

@@ -6,10 +6,10 @@ describe('Two-way binding e2e tests', () => {
     browser.get('');
   });
 
-  let minusButton = element.all(by.css('button')).get(0);
+  const minusButton = element.all(by.css('button')).get(0);
-  let plusButton = element.all(by.css('button')).get(1);
+  const plusButton = element.all(by.css('button')).get(1);
-  let minus2Button = element.all(by.css('button')).get(2);
+  const minus2Button = element.all(by.css('button')).get(2);
-  let plus2Button = element.all(by.css('button')).get(3);
+  const plus2Button = element.all(by.css('button')).get(3);
 
   it('should display Two-way Binding', () => {
     expect(element(by.css('h1')).getText()).toEqual('Two-way Binding');

aio/content/examples/upgrade-lazy-load-ajs/e2e/src/app.e2e-spec.ts

@@ -57,7 +57,7 @@ describe('Lazy Loading AngularJS Tests', () => {
     // Run the protractor pre-bootstrap logic and resumeBootstrap
     // Based on https://github.com/angular/protractor/blob/5.3.0/lib/browser.ts#L950-L969
     {
-        let moduleNames = [];
+        const moduleNames = [];
         for (const {name, script, args} of browser.mockModules_) {
             moduleNames.push(name);
             await browser.executeScriptWithDescription(script, 'add mock module ' + name, ...args);

aio/content/examples/upgrade-phonecat-1-typescript/app/core/phone/phone.service.spec.ts

@@ -2,7 +2,7 @@
 describe('Phone', () => {
   let $httpBackend: angular.IHttpBackendService;
   let Phone: any;
-  let phonesData = [
+  const phonesData = [
     {name: 'Phone X'},
     {name: 'Phone Y'},
     {name: 'Phone Z'}
@@ -31,7 +31,7 @@ describe('Phone', () => {
   });
 
   it('should fetch the phones data from `/phones/phones.json`', () => {
-    let phones = Phone.query();
+    const phones = Phone.query();
 
     expect(phones).toEqual([]);
 

aio/content/examples/upgrade-phonecat-1-typescript/app/phone-detail/phone-detail.component.spec.ts

@@ -9,7 +9,7 @@ describe('phoneDetail', () => {
   describe('PhoneDetailController', () => {
     let $httpBackend: angular.IHttpBackendService;
     let ctrl: any;
-    let xyzPhoneData = {
+    const xyzPhoneData = {
       name: 'phone xyz',
       images: ['image/url1.png', 'image/url2.png']
     };

aio/content/examples/upgrade-phonecat-1-typescript/app/phone-detail/phone-detail.component.ts

@@ -6,7 +6,7 @@ class PhoneDetailController {
 
   static $inject = ['$routeParams', 'Phone'];
   constructor($routeParams: angular.route.IRouteParamsService, Phone: any) {
-    let phoneId = $routeParams.phoneId;
+    const phoneId = $routeParams.phoneId;
     this.phone = Phone.get({phoneId}, (phone: any) => {
       this.setImage(phone.images[0]);
     });

aio/content/examples/upgrade-phonecat-1-typescript/e2e-spec.ts

@@ -29,8 +29,8 @@ describe('PhoneCat Application', () => {
     });
 
     it('should filter the phone list as a user types into the search box', () => {
-      let phoneList = element.all(by.repeater('phone in $ctrl.phones'));
+      const phoneList = element.all(by.repeater('phone in $ctrl.phones'));
-      let query = element(by.model('$ctrl.query'));
+      const query = element(by.model('$ctrl.query'));
 
       waitForCount(phoneList, 20);
       expect(phoneList.count()).toBe(20);
@@ -46,10 +46,10 @@ describe('PhoneCat Application', () => {
     });
 
     it('should be possible to control phone order via the drop-down menu', () => {
-      let queryField = element(by.model('$ctrl.query'));
+      const queryField = element(by.model('$ctrl.query'));
-      let orderSelect = element(by.model('$ctrl.orderProp'));
+      const orderSelect = element(by.model('$ctrl.orderProp'));
-      let nameOption = orderSelect.element(by.css('option[value="name"]'));
+      const nameOption = orderSelect.element(by.css('option[value="name"]'));
-      let phoneNameColumn = element.all(by.repeater('phone in $ctrl.phones').column('phone.name'));
+      const phoneNameColumn = element.all(by.repeater('phone in $ctrl.phones').column('phone.name'));
 
       function getNames() {
         return phoneNameColumn.map((elem: ElementFinder) => elem.getText());
@@ -72,14 +72,14 @@ describe('PhoneCat Application', () => {
     });
 
     it('should render phone specific links', () => {
-      let phoneList = element.all(by.repeater('phone in $ctrl.phones'));
+      const phoneList = element.all(by.repeater('phone in $ctrl.phones'));
-      let query = element(by.model('$ctrl.query'));
+      const query = element(by.model('$ctrl.query'));
 
       query.sendKeys('nexus');
       waitForCount(phoneList, 1);
 
-      let nexusPhone = phoneList.first();
+      const nexusPhone = phoneList.first();
-      let detailLink = nexusPhone.all(by.css('a')).first();
+      const detailLink = nexusPhone.all(by.css('a')).first();
 
       detailLink.click();
       expect(browser.getLocationAbsUrl()).toBe('/phones/nexus-s');
@@ -98,14 +98,14 @@ describe('PhoneCat Application', () => {
     });
 
     it('should display the first phone image as the main phone image', () => {
-      let mainImage = element(by.css('img.phone.selected'));
+      const mainImage = element(by.css('img.phone.selected'));
 
       expect(mainImage.getAttribute('src')).toMatch(/img\/phones\/nexus-s.0.jpg/);
     });
 
     it('should swap the main image when clicking on a thumbnail image', () => {
-      let mainImage = element(by.css('img.phone.selected'));
+      const mainImage = element(by.css('img.phone.selected'));
-      let thumbnails = element.all(by.css('.phone-thumbs img'));
+      const thumbnails = element.all(by.css('.phone-thumbs img'));
 
       thumbnails.get(2).click();
       expect(mainImage.getAttribute('src')).toMatch(/img\/phones\/nexus-s.2.jpg/);

aio/content/examples/upgrade-phonecat-2-hybrid/app/core/phone/phone.service.spec.ts

@@ -6,7 +6,7 @@ import { Phone, PhoneData } from './phone.service';
 
 describe('Phone', () => {
   let phone: Phone;
-  let phonesData: PhoneData[] = [
+  const phonesData: PhoneData[] = [
     {name: 'Phone X', snippet: '', images: []},
     {name: 'Phone Y', snippet: '', images: []},
     {name: 'Phone Z', snippet: '', images: []}

aio/content/examples/upgrade-phonecat-2-hybrid/app/phone-detail/phone-detail.component.ajs.ts

@@ -9,7 +9,7 @@ class PhoneDetailController {
 
   static $inject = ['$routeParams', 'phone'];
   constructor($routeParams: angular.route.IRouteParamsService, phone: Phone) {
-    let phoneId = $routeParams.phoneId;
+    const phoneId = $routeParams.phoneId;
     phone.get(phoneId).subscribe(data => {
       this.phone = data;
       this.setImage(data.images[0]);