docs: add forms overview example for snippets (#25663)

PR Close #25663

aio/content/examples/forms-overview/src/app/app.component.html

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+<!--The content below is only a placeholder and can be replaced.-->
+<h1>Forms Overview</h1>
+
+<h2>Reactive</h2>
+
+<app-reactive-name></app-reactive-name>
+
+<h2>Template-Driven</h2>
+
+<app-template-name></app-template-name>

aio/content/examples/forms-overview/src/app/app.component.spec.ts

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+import { TestBed, async } from '@angular/core/testing';
+import { AppComponent } from './app.component';
+import { TemplateModule } from './template/template.module';
+import { ReactiveModule } from './reactive/reactive.module';
+
+describe('AppComponent', () => {
+
+  beforeEach(async(() => {
+    TestBed.configureTestingModule({
+      imports: [ReactiveModule, TemplateModule],
+      declarations: [
+        AppComponent
+      ],
+    }).compileComponents();
+  }));
+
+  it('should create the app', async(() => {
+    const fixture = TestBed.createComponent(AppComponent);
+    const app = fixture.debugElement.componentInstance;
+
+    expect(app).toBeTruthy();
+  }));
+
+  it('should render title in a h1 tag', async(() => {
+    const fixture = TestBed.createComponent(AppComponent);
+    fixture.detectChanges();
+
+    const compiled = fixture.debugElement.nativeElement;
+    expect(compiled.querySelector('h1').textContent).toContain('Forms Overview');
+  }));
+});

aio/content/examples/forms-overview/src/app/app.component.ts

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+import { Component } from '@angular/core';
+
+@Component({
+  selector: 'app-root',
+  templateUrl: './app.component.html',
+  styleUrls: ['./app.component.css']
+})
+export class AppComponent {
+  title = 'forms-intro';
+}

aio/content/examples/forms-overview/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 { ReactiveModule } from './reactive/reactive.module';
+import { TemplateModule } from './template/template.module';
+
+@NgModule({
+  declarations: [
+    AppComponent,
+  ],
+  imports: [
+    BrowserModule,
+    ReactiveModule,
+    TemplateModule
+  ],
+  providers: [],
+  bootstrap: [AppComponent]
+})
+export class AppModule { }

aio/content/examples/forms-overview/src/app/reactive/name/name.component.spec.ts

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+// #docregion
+import { async, ComponentFixture, TestBed } from '@angular/core/testing';
+import { ReactiveFormsModule } from '@angular/forms';
+
+import { ReactiveNameComponent } from './name.component';
+import { createNewEvent } from '../../shared/utils';
+
+// #docregion tests
+describe('Reactive Name Component', () => {
+// #enddocregion tests
+  let component: ReactiveNameComponent;
+  let fixture: ComponentFixture<ReactiveNameComponent>;
+
+  beforeEach(async(() => {
+    TestBed.configureTestingModule({
+      imports: [ReactiveFormsModule],
+      declarations: [ReactiveNameComponent]
+    })
+    .compileComponents();
+  }));
+
+  beforeEach(() => {
+    fixture = TestBed.createComponent(ReactiveNameComponent);
+    component = fixture.componentInstance;
+    fixture.detectChanges();
+  });
+
+  it('should create', () => {
+    expect(component).toBeTruthy();
+  });
+
+// #docregion tests
+  it('should update the value in the control', () => {
+    // update the control value
+    component.name.setValue('Nancy');
+
+    // query the element
+    const input = fixture.nativeElement.querySelector('input');
+
+    // check its value
+    expect(input.value).toBe('Nancy');
+  });
+
+  it('should update the value of the input field', () => {
+    // update the control value
+    component.name.setValue('Nancy');
+
+    // query the element
+    const input = fixture.nativeElement.querySelector('input');
+    expect(input.value).toEqual('Nancy');
+
+    // update the form field value
+    input.value = 'Smith';
+
+    // Use utility function to create custom event, then dispatch on the input
+    const event = createNewEvent('input');
+    input.dispatchEvent(event);
+
+    expect(fixture.componentInstance.name.value).toEqual('Smith');
+  });
+});
+// #enddocregion

aio/content/examples/forms-overview/src/app/reactive/name/name.component.ts

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+// #docplaster
+// #docregion
+import { Component } from '@angular/core';
+import { FormControl } from '@angular/forms';
+
+@Component({
+// #enddocregion
+  selector: 'app-reactive-name',
+// #docregion
+  template: `
+    Name: <input type="text" [formControl]="name">
+  `
+})
+export class ReactiveNameComponent {
+  name = new FormControl('');
+}
+// #enddocregion

aio/content/examples/forms-overview/src/app/reactive/reactive.module.spec.ts

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+import { ReactiveModule } from './reactive.module';
+
+describe('ReactiveModule', () => {
+  let reactiveModule: ReactiveModule;
+
+  beforeEach(() => {
+    reactiveModule = new ReactiveModule();
+  });
+
+  it('should create an instance', () => {
+    expect(reactiveModule).toBeTruthy();
+  });
+});

aio/content/examples/forms-overview/src/app/reactive/reactive.module.ts

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+import { NgModule } from '@angular/core';
+import { CommonModule } from '@angular/common';
+import { ReactiveNameComponent } from './name/name.component';
+import { ReactiveFormsModule } from '@angular/forms';
+
+@NgModule({
+  imports: [
+    CommonModule,
+    ReactiveFormsModule
+  ],
+  declarations: [ReactiveNameComponent],
+  exports: [ReactiveNameComponent],
+})
+export class ReactiveModule { }

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

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

aio/content/examples/forms-overview/src/app/template/name/name.component.spec.ts

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+// #docregion
+import { async, ComponentFixture, TestBed, tick, fakeAsync } from '@angular/core/testing';
+import { FormsModule } from '@angular/forms';
+
+import { createNewEvent } from '../../shared/utils';
+import { TemplateNameComponent } from './name.component';
+
+// #docregion tests
+describe('Template Name Component', () => {
+// #enddocregion tests
+  let component: TemplateNameComponent;
+  let fixture: ComponentFixture<TemplateNameComponent>;
+
+  beforeEach(async(() => {
+    TestBed.configureTestingModule({
+      imports: [FormsModule],
+      declarations: [TemplateNameComponent]
+    })
+    .compileComponents();
+  }));
+
+  beforeEach(() => {
+    fixture = TestBed.createComponent(TemplateNameComponent);
+    component = fixture.componentInstance;
+    fixture.detectChanges();
+  });
+
+  it('should create', () => {
+    expect(component).toBeTruthy();
+  });
+
+// #docregion tests
+  it('should update the value in the control', fakeAsync(() => {
+    // update the component instance variable
+    component.name = 'Nancy';
+
+    // run change detection
+    fixture.detectChanges();
+
+    // advance after change detection cycle
+    tick();
+
+    // query the element
+    const input = fixture.nativeElement.querySelector('input');
+
+    expect(input.value).toBe('Nancy');
+  }));
+
+  it('should update the value of the input field', fakeAsync(() => {
+    // update component instance variable
+    component.name = 'Nancy';
+
+    // run change detection
+    fixture.detectChanges();
+
+    // advance after change detection cycle
+    tick();
+
+    // query the element
+    const input = fixture.nativeElement.querySelector('input');
+    expect(input.value).toEqual('Nancy');
+
+    // update the form field value
+    input.value = 'Smith';
+
+    // Use utility function to create custom event, then dispatch on the input
+    const event = createNewEvent('input');
+    input.dispatchEvent(event);
+
+    // advance after change detection cycle
+    tick();
+
+    expect(component.name).toEqual('Smith');
+  }));
+});
+// #enddocregion

aio/content/examples/forms-overview/src/app/template/name/name.component.ts

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+// #docplaster
+// #docregion
+import { Component } from '@angular/core';
+
+@Component({
+// #enddocregion
+  selector: 'app-template-name',
+// #docregion
+  template: `
+    Name: <input type="text" [(ngModel)]="name">
+  `
+})
+export class TemplateNameComponent {
+  name = '';
+}
+// #enddocregion

aio/content/examples/forms-overview/src/app/template/template.module.spec.ts

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+import { TemplateModule } from './template.module';
+
+describe('TemplateModule', () => {
+  let templateModule: TemplateModule;
+
+  beforeEach(() => {
+    templateModule = new TemplateModule();
+  });
+
+  it('should create an instance', () => {
+    expect(templateModule).toBeTruthy();
+  });
+});

aio/content/examples/forms-overview/src/app/template/template.module.ts

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+import { NgModule } from '@angular/core';
+import { CommonModule } from '@angular/common';
+import { TemplateNameComponent } from './name/name.component';
+import { FormsModule } from '@angular/forms';
+
+@NgModule({
+  imports: [
+    CommonModule,
+    FormsModule
+  ],
+  declarations: [TemplateNameComponent],
+  exports: [TemplateNameComponent]
+})
+export class TemplateModule { }

aio/content/examples/forms-overview/src/index.html

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+<!doctype html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <title>Forms Overview</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/forms-overview/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));