docs: drop `newEvent()` compatibility function (#37251)

Because PhantomJS has been deprecated since March 2018, and `newEvent`
is very confusing for newcomers that read the testing documentation,
we remove it entirely, and instead assume most, if not all, newcomers
will run tests in Chrome as it is the default.

Fixes #23370

PR Close #37251

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

@@ -28,7 +28,7 @@ import {
   ComponentFixture, fakeAsync, inject, TestBed, tick, waitForAsync
 } from '@angular/core/testing';
 
-import { addMatchers, newEvent, click } from '../../testing';
+import { addMatchers, click } from '../../testing';
 
 export class NotProvided extends ValueService { /* example below */ }
 beforeEach(addMatchers);
@@ -274,9 +274,11 @@ describe('demo (with TestBed):', () => {
         expect(comp.name).toBe(expectedOrigName,
           `comp.name should still be ${expectedOrigName} after value change, before binding happens`);
 
-        // dispatch a DOM event so that Angular learns of input value change.
+        // Dispatch a DOM event so that Angular learns of input value change.
         // then wait while ngModel pushes input.box value to comp.name
-        input.dispatchEvent(newEvent('input'));
+        // In older browsers, such as IE, you might need a CustomEvent instead. See
+        // https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent/CustomEvent#Polyfill
+        input.dispatchEvent(new Event('input'));
         return fixture.whenStable();
       })
         .then(() => {
@@ -312,9 +314,11 @@ describe('demo (with TestBed):', () => {
       expect(comp.name).toBe(expectedOrigName,
         `comp.name should still be ${expectedOrigName} after value change, before binding happens`);
 
-      // dispatch a DOM event so that Angular learns of input value change.
+      // Dispatch a DOM event so that Angular learns of input value change.
       // then wait a tick while ngModel pushes input.box value to comp.name
-      input.dispatchEvent(newEvent('input'));
+      // In older browsers, such as IE, you might need a CustomEvent instead. See
+      // https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent/CustomEvent#Polyfill
+      input.dispatchEvent(new Event('input'));
       tick();
       expect(comp.name).toBe(expectedNewName,
         `After ngModel updates the model, comp.name should be ${expectedNewName} `);
@@ -335,10 +339,12 @@ describe('demo (with TestBed):', () => {
       // simulate user entering new name in input
       input.value = inputText;
 
-      // dispatch a DOM event so that Angular learns of input value change.
+      // Dispatch a DOM event so that Angular learns of input value change.
       // then wait a tick while ngModel pushes input.box value to comp.text
       // and Angular updates the output span
-      input.dispatchEvent(newEvent('input'));
+      // In older browsers, such as IE, you might need a CustomEvent instead. See
+      // https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent/CustomEvent#Polyfill
+      input.dispatchEvent(new Event('input'));
       tick();
       fixture.detectChanges();
       expect(span.textContent).toBe(expectedText, 'output span');

aio/content/examples/testing/src/app/hero/hero-detail.component.spec.ts

@@ -3,7 +3,7 @@ import { ComponentFixture, fakeAsync, inject, TestBed, tick, waitForAsync } from
 import { Router } from '@angular/router';
 
 import {
-  ActivatedRoute, ActivatedRouteStub, asyncData, click, newEvent
+  ActivatedRoute, ActivatedRouteStub, asyncData, click
 } from '../../testing';
 
 import { Hero } from '../model/hero';
@@ -99,7 +99,10 @@ function overrideSetup() {
        const newName = 'New Name';
 
        page.nameInput.value = newName;
-       page.nameInput.dispatchEvent(newEvent('input'));  // tell Angular
+
+       // In older browsers, such as IE, you might need a CustomEvent instead. See
+       // https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent/CustomEvent#Polyfill
+       page.nameInput.dispatchEvent(new Event('input')); // tell Angular
 
        expect(component.hero.name).toBe(newName, 'component hero has new name');
        expect(hdsSpy.testHero.name).toBe(origName, 'service hero unchanged before save');
@@ -197,9 +200,10 @@ function heroModuleSetup() {
       // simulate user entering a new name into the input box
       nameInput.value = 'quick BROWN  fOx';
 
-      // dispatch a DOM event so that Angular learns of input value change.
-      // use newEvent utility function (not provided by Angular) for better browser compatibility
-      nameInput.dispatchEvent(newEvent('input'));
+      // Dispatch a DOM event so that Angular learns of input value change.
+      // In older browsers, such as IE, you might need a CustomEvent instead. See
+      // https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent/CustomEvent#Polyfill
+      nameInput.dispatchEvent(new Event('input'));
 
       // Tell Angular to update the display binding through the title pipe
       fixture.detectChanges();

aio/content/examples/testing/src/app/hero/hero-list.component.spec.ts

@@ -6,7 +6,7 @@ import { DebugElement } from '@angular/core';
 
 import { Router } from '@angular/router';
 
-import { addMatchers, newEvent } from '../../testing';
+import { addMatchers } from '../../testing';
 import { HeroService } from '../model/hero.service';
 import { getTestHeroes, TestHeroService } from '../model/testing/test-hero.service';
 
@@ -53,7 +53,10 @@ describe('HeroListComponent', () => {
   it('should select hero on click', fakeAsync(() => {
        const expectedHero = HEROES[1];
        const li = page.heroRows[1];
-       li.dispatchEvent(newEvent('click'));
+
+       // In older browsers, such as IE, you might need a CustomEvent instead. See
+       // https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent/CustomEvent#Polyfill
+       li.dispatchEvent(new Event('click'));
        tick();
        // `.toEqual` because selectedHero is clone of expectedHero; see FakeHeroService
        expect(comp.selectedHero).toEqual(expectedHero);
@@ -62,7 +65,10 @@ describe('HeroListComponent', () => {
   it('should navigate to selected hero detail on click', fakeAsync(() => {
        const expectedHero = HEROES[1];
        const li = page.heroRows[1];
-       li.dispatchEvent(newEvent('click'));
+
+       // In older browsers, such as IE, you might need a CustomEvent instead. See
+       // https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent/CustomEvent#Polyfill
+       li.dispatchEvent(new Event('click'));
        tick();
 
        // should have navigated

aio/content/examples/testing/src/app/shared/highlight.directive.spec.ts

@@ -3,7 +3,6 @@ import { ComponentFixture, TestBed } from '@angular/core/testing';
 import { By } from '@angular/platform-browser';
 
 import { HighlightDirective } from './highlight.directive';
-import { newEvent } from '../../testing';
 
 // #docregion test-component
 @Component({
@@ -59,9 +58,12 @@ describe('HighlightDirective', () => {
     const input = des[2].nativeElement as HTMLInputElement;
     expect(input.style.backgroundColor).toBe('cyan', 'initial backgroundColor');
 
-    // dispatch a DOM event so that Angular responds to the input value change.
     input.value = 'green';
-    input.dispatchEvent(newEvent('input'));
+
+    // Dispatch a DOM event so that Angular responds to the input value change.
+    // In older browsers, such as IE, you might need a CustomEvent instead. See
+    // https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent/CustomEvent#Polyfill
+    input.dispatchEvent(new Event('input'));
     fixture.detectChanges();
 
     expect(input.style.backgroundColor).toBe('green', 'changed backgroundColor');

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

@@ -14,18 +14,6 @@ export function advance(f: ComponentFixture<any>): void {
   f.detectChanges();
 }
 
-/**
- * Create custom DOM event the old fashioned way
- *
- * https://developer.mozilla.org/en-US/docs/Web/API/Event/initEvent
- * Although officially deprecated, some browsers (phantom) don't accept the preferred "new Event(eventName)"
- */
-export function newEvent(eventName: string, bubbles = false, cancelable = false) {
-  const evt = document.createEvent('CustomEvent');  // MUST be 'CustomEvent'
-  evt.initCustomEvent(eventName, bubbles, cancelable, null);
-  return evt;
-}
-
 // See https://developer.mozilla.org/en-US/docs/Web/API/MouseEvent/button
 // #docregion click-event
 /** Button events to pass to `DebugElement.triggerEventHandler` for RouterLink event handler */