docs: rewrite event binding section and add example (#26162)

PR Close #26162

aio/content/examples/event-binding/src/app/app.component.css

@@ -0,0 +1,25 @@
+.group {
+  background-color: #dae8f9;
+  padding: 1rem;
+  margin: 1rem 0;
+}
+
+.parent-div {
+  background-color: #bdd1f7;
+  border: solid 1px rgb(25, 118, 210);
+  padding: 1rem;
+}
+
+.parent-div:hover {
+  background-color: #8fb4f9;
+}
+
+.child-div {
+  margin-top: 1rem;
+  background-color: #fff;
+  padding: 1rem;
+}
+
+.child-div:hover {
+  background-color: #eee;
+}

aio/content/examples/event-binding/src/app/app.component.html

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+<h1 id="event-binding">Event Binding</h1>
+
+<div class="group">
+  <h3>Target event</h3>
+  <!-- #docregion event-binding-1 -->
+  <button (click)="onSave($event)">Save</button>
+  <!-- #enddocregion event-binding-1 -->
+
+  <!-- #docregion event-binding-2 -->
+  <button on-click="onSave($event)">on-click Save</button>
+  <!-- #enddocregion event-binding-2 -->
+
+  <!-- #docregion custom-directive -->
+  <h4>myClick is an event on the custom ClickDirective:</h4>
+  <button (myClick)="clickMessage=$event" clickable>click with myClick</button>
+  {{clickMessage}}
+  <!-- #enddocregion custom-directive -->
+
+</div>
+
+<div class="group">
+  <h3>$event and event handling statements</h3>
+  <h4>Result: {{currentItem.name}}</h4>
+
+  <!-- #docregion event-binding-3-->
+  <input [value]="currentItem.name"
+         (input)="currentItem.name=$event.target.value" >
+  without NgModel
+  <!-- #enddocregion event-binding-3-->
+</div>
+
+<div class="group">
+  <h3>Binding to a nested component</h3>
+  <h4>Custom events with EventEmitter</h4>
+  <!-- #docregion event-binding-to-component -->
+  <app-item-detail (deleteRequest)="deleteItem($event)" [item]="currentItem"></app-item-detail>
+    <!-- #enddocregion event-binding-to-component -->
+
+
+  <h4>Click to see event target class:</h4>
+<div class="parent-div" (click)="onClickMe($event)" clickable>Click me (parent)
+  <div class="child-div">Click me too! (child) </div>
+</div>
+
+<h3>Saves only once:</h3>
+<div (click)="onSave()" clickable>
+  <button (click)="onSave($event)">Save, no propagation</button>
+</div>
+
+<h3>Saves twice:</h3>
+<div (click)="onSave()" clickable>
+  <button (click)="onSave()">Save with propagation</button>
+</div>

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

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+import { TestBed, async } from '@angular/core/testing';
+import { AppComponent } from './app.component';
+describe('AppComponent', () => {
+  beforeEach(async(() => {
+    TestBed.configureTestingModule({
+      declarations: [
+        AppComponent
+      ],
+    }).compileComponents();
+  }));
+  it('should create the app', async(() => {
+    const fixture = TestBed.createComponent(AppComponent);
+    const app = fixture.debugElement.componentInstance;
+    expect(app).toBeTruthy();
+  }));
+  it(`should have as title 'Featured product:'`, async(() => {
+    const fixture = TestBed.createComponent(AppComponent);
+    const app = fixture.debugElement.componentInstance;
+    expect(app.title).toEqual('Featured product:');
+  }));
+  it('should render title in a p tag', async(() => {
+    const fixture = TestBed.createComponent(AppComponent);
+    fixture.detectChanges();
+    const compiled = fixture.debugElement.nativeElement;
+    expect(compiled.querySelector('p').textContent).toContain('Featured product:');
+  }));
+});

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

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+import { Component } from '@angular/core';
+import { Item } from './item';
+
+@Component({
+  selector: 'app-root',
+  templateUrl: './app.component.html',
+  styleUrls: ['./app.component.css']
+})
+export class AppComponent {
+
+  currentItem = { name: 'teapot'} ;
+  clickMessage = '';
+
+  onSave(event: KeyboardEvent) {
+    const evtMsg = event ? ' Event target is ' + (<HTMLElement>event.target).textContent : '';
+    alert('Saved.' + evtMsg);
+    if (event) { event.stopPropagation(); }
+  }
+
+  deleteItem(item: Item) {
+    alert(`Delete the ${item}.`);
+  }
+
+  onClickMe(event: KeyboardEvent) {
+    const evtMsg = event ? ' Event target class is ' + (<HTMLElement>event.target).className  : '';
+    alert('Click me.' + evtMsg);
+  }
+
+}

aio/content/examples/event-binding/src/app/app.module.ts

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+import { BrowserModule } from '@angular/platform-browser';
+import { NgModule } from '@angular/core';
+
+
+import { AppComponent } from './app.component';
+import { ItemDetailComponent } from './item-detail/item-detail.component';
+import { ClickDirective } from './click.directive';
+
+
+@NgModule({
+  declarations: [
+    AppComponent,
+    ItemDetailComponent,
+    ClickDirective
+  ],
+  imports: [
+    BrowserModule
+  ],
+  providers: [],
+  bootstrap: [AppComponent]
+})
+export class AppModule { }

aio/content/examples/event-binding/src/app/click.directive.ts

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+/* tslint:disable use-output-property-decorator directive-class-suffix */
+import { Directive, ElementRef, EventEmitter, Output } from '@angular/core';
+
+@Directive({selector: '[myClick]'})
+export class ClickDirective {
+  @Output('myClick') clicks = new EventEmitter<string>(); //  @Output(alias) propertyName = ...
+
+  toggle = false;
+
+  constructor(el: ElementRef) {
+    el.nativeElement
+      .addEventListener('click', (event: Event) => {
+        this.toggle = !this.toggle;
+        this.clicks.emit(this.toggle ? 'Click!' : '');
+      });
+  }
+}
+

aio/content/examples/event-binding/src/app/item-detail/item-detail.component.css

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+.detail {
+  border: 1px solid rgb(25, 118, 210);
+  padding: 1rem;
+  margin: 1rem 0;
+}
+
+img {
+  max-width: 100px;
+  display: block;
+  padding: 1rem 0;
+}

aio/content/examples/event-binding/src/app/item-detail/item-detail.component.html

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+<div class="detail">
+  <p>This is the ItemDetailComponent</p>
+  <!-- #docregion line-through -->
+  <img src="{{itemImageUrl}}" [style.display]="displayNone">
+  <span [style.text-decoration]="lineThrough">{{ item.name }}
+  </span>
+  <button (click)="delete()">Delete</button>
+  <!-- #enddocregion line-through -->
+</div>

aio/content/examples/event-binding/src/app/item-detail/item-detail.component.spec.ts

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+import { async, ComponentFixture, TestBed } from '@angular/core/testing';
+
+import { ItemDetailComponent } from './item-detail.component';
+
+describe('ItemDetailComponent', () => {
+  let component: ItemDetailComponent;
+  let fixture: ComponentFixture<ItemDetailComponent>;
+
+  beforeEach(async(() => {
+    TestBed.configureTestingModule({
+      declarations: [ ItemDetailComponent ]
+    })
+    .compileComponents();
+  }));
+
+  beforeEach(() => {
+    fixture = TestBed.createComponent(ItemDetailComponent);
+    component = fixture.componentInstance;
+    fixture.detectChanges();
+  });
+
+  it('should create', () => {
+    expect(component).toBeTruthy();
+  });
+});

aio/content/examples/event-binding/src/app/item-detail/item-detail.component.ts

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+/* tslint:disable use-input-property-decorator use-output-property-decorator */
+import { Component, EventEmitter, Input, Output } from '@angular/core';
+
+import { Item } from '../item';
+
+@Component({
+  selector: 'app-item-detail',
+  styleUrls: ['./item-detail.component.css'],
+  templateUrl: './item-detail.component.html'
+})
+export class ItemDetailComponent {
+
+  @Input() item;
+  itemImageUrl = 'assets/teapot.svg';
+  lineThrough = '';
+  displayNone = '';
+  @Input() prefix = '';
+
+  // #docregion deleteRequest
+  // This component makes a request but it can't actually delete a hero.
+  @Output() deleteRequest = new EventEmitter<Item>();
+
+  delete() {
+    this.deleteRequest.emit(this.item.name);
+    this.displayNone = this.displayNone ? '' : 'none';
+    this.lineThrough = this.lineThrough ? '' : 'line-through';
+  }
+  // #enddocregion deleteRequest
+
+}

aio/content/examples/event-binding/src/app/item.ts

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+export class Item {
+  name: '';
+}
+

aio/content/examples/event-binding/src/index.html

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+<!doctype html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <title>EventBinding</title>
+  <base href="/">
+
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <link rel="icon" type="image/x-icon" href="favicon.ico">
+</head>
+<body>
+  <app-root></app-root>
+</body>
+</html>

aio/content/examples/event-binding/src/main.ts

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+import { enableProdMode } from '@angular/core';
+import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
+
+import { AppModule } from './app/app.module';
+import { environment } from './environments/environment';
+
+if (environment.production) {
+  enableProdMode();
+}
+
+platformBrowserDynamic().bootstrapModule(AppModule)
+  .catch(err => console.log(err));