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/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;
-  let car = new Car(new Engine2(bigCylinders), new Tires());
+  const bigCylinders = 12;
+  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);
-let bob = new User('Bob', false);
+const alice = new User('Alice', true);
+const bob = new User('Bob', false);
 
 @Injectable({
   providedIn: 'root'