Here are a few possible titles: 1. How to Make CSS Transitions Work with `ngIf` in Angular 2? 2. Why Does `ngIf` Break My CSS Transitions in Angular 2? 3. Angular 2: Combining `ngIf` and CSS Animations for Smooth Trans

ngIf and CSS Transitions/Animations for Angular 2

How to slide a div in from the right using CSS in Angular 2?

<code class="html"><div class="note" [ngClass]="{'transition':show}" *ngIf="show">
  <p> Notes</p>
</div>
<button class="btn btn-default" (click)="toggle(show)">Toggle</button></code>

.transition{
  -webkit-transition: opacity 1000ms ease-in-out,margin-left 500ms ease-in-out;
  -moz-transition: opacity 1000ms ease-in-out,margin-left 500ms ease-in-out;
  -ms-transition: opacity 1000ms ease-in-out,margin-left 500ms ease-in-out ;
  -o-transition: opacity 1000ms ease-in-out,margin-left 500ms ease-in-out;
  transition: opacity 1000ms ease-in-out,margin-left 500ms ease-in-out;
  margin-left: 1500px;
  width: 200px;
  opacity: 0;
}

.transition{
  opacity: 100;
  margin-left: 0;
}

If you just use [ngClass] to switch classes, and take advantage of opacity, this code works fine. But don't want that element to be rendered from the beginning, so I "hide" it with ngIf first, but then the transition won't work.

Update 4.1.0

Uses the transition animation API, no need to use [hidden] or [*ngIf hidden] anymore.

Updated 2.1.0

View animation on angular.io

<code class="typescript">import { trigger, style, animate, transition } from '@angular/animations';

@Component({
  selector: 'my-app',
  animations: [
    trigger(
      'enterAnimation', [
        transition(':enter', [
          style({transform: 'translateX(100%)', opacity: 0}),
          animate('500ms', style({transform: 'translateX(0)', opacity: 1}))
        ]),
        transition(':leave', [
          style({transform: 'translateX(0)', opacity: 1}),
          animate('500ms', style({transform: 'translateX(100%)', opacity: 0}))
        ])
      ]
    )
  ],
  template: `
    <button (click)="show = !show">toggle show ({{show}})</button>

    <div *ngIf="show" [@enterAnimation]>xxx</div>
  `
})
export class App {
  show:boolean = false;
}</code>

Original answer

When the expression becomes false, *ngIf will remove the element from the DOM. A non-existent element cannot be transitioned.

can be replaced by the hidden attribute:

<code class="html"><div class="note" [ngClass]="{'transition':show}" [hidden]="!show"></code>

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