[angular] Angular (4, 5, 6, 7) - Simple example of slide in out animation on ngIf

What is the bare minimum and Angular4's native way to slide in and slide out a container element?

e.g.

<div ngIf="show">
    <!-- Content -->
</div>

Slide In Content (from top to down just like jQuery.slideDown()) when show turns to true.

Slide Out Content (suitably with ease-out effect) when show turns to false.

The most upvoted answer is not implementing a real slide in/out (or down/up), as:

1. It's not doing a soft transition on the height attribute. At time zero the element already has the 100% of its height producing a sudden glitch on the elements below it.
2. When sliding out/up, the element does a translateY(-100%) and then suddenly disappears, causing another glitch on the elements below it.

You can implement a slide in and slide out like so:

my-component.ts

import { animate, style, transition, trigger } from '@angular/animations';

@Component({
  ...
  animations: [
    trigger('slideDownUp', [
      transition(':enter', [style({ height: 0 }), animate(500)]),
      transition(':leave', [animate(500, style({ height: 0 }))]),
    ]),
  ],
})

my-component.html

<div @slideDownUp *ngIf="isShowing" class="box">
  I am the content of the div!
</div>

my-component.scss

.box {
  overflow: hidden;
}

Actually the minimum amount of Angular to be used (as requested in the original question) is just adding a class to the DOM element when show variable is true, and perform the animation/transition via CSS.

So your minimum Angular code is this:

<div class="box-opener" (click)="show = !show">
    Open/close the box
</div>

<div class="box" [class.opened]="show">
    <!-- Content -->
</div>

With this solution, you need to create CSS rules for the transition, something like this:

.box {
    background-color: #FFCC55;
    max-height: 0px;
    overflow-y: hidden;
    transition: ease-in-out 400ms max-height;
}

.box.opened {
    max-height: 500px;
    transition: ease-in-out 600ms max-height;
}

If you have retro-browser-compatibility issues, just remember to add the vendor prefixes in the transitions.

See the example here

I answered a very similar question, and here is a way of doing this :

First, create a file where you would define your animations and export them. Just to make it more clear in your app.component.ts

In the following example, I used a max-height of the div that goes from 0px (when it's hidden), to 500px, but you would change that according to what you need.

This animation uses states (in and out), that will be toggle when we click on the button, which will run the animtion.

animations.ts

import { trigger, state, style, transition,
    animate, group, query, stagger, keyframes
} from '@angular/animations';

export const SlideInOutAnimation = [
    trigger('slideInOut', [
        state('in', style({
            'max-height': '500px', 'opacity': '1', 'visibility': 'visible'
        })),
        state('out', style({
            'max-height': '0px', 'opacity': '0', 'visibility': 'hidden'
        })),
        transition('in => out', [group([
            animate('400ms ease-in-out', style({
                'opacity': '0'
            })),
            animate('600ms ease-in-out', style({
                'max-height': '0px'
            })),
            animate('700ms ease-in-out', style({
                'visibility': 'hidden'
            }))
        ]
        )]),
        transition('out => in', [group([
            animate('1ms ease-in-out', style({
                'visibility': 'visible'
            })),
            animate('600ms ease-in-out', style({
                'max-height': '500px'
            })),
            animate('800ms ease-in-out', style({
                'opacity': '1'
            }))
        ]
        )])
    ]),
]

Then in your app.component, we import the animation and create the method that will toggle the animation state.

app.component.ts

import { SlideInOutAnimation } from './animations';

@Component({
  ...
  animations: [SlideInOutAnimation]
})
export class AppComponent  {
  animationState = 'in';

  ...

  toggleShowDiv(divName: string) {
    if (divName === 'divA') {
      console.log(this.animationState);
      this.animationState = this.animationState === 'out' ? 'in' : 'out';
      console.log(this.animationState);
    }
  }
}

And here is how your app.component.html would look like :

<div class="wrapper">
  <button (click)="toggleShowDiv('divA')">TOGGLE DIV</button>
  <div [@slideInOut]="animationState" style="height: 100px; background-color: red;">
  THIS DIV IS ANIMATED</div>
  <div class="content">THIS IS CONTENT DIV</div>
</div>

slideInOut refers to the animation trigger defined in animations.ts

Here is a StackBlitz example I have created : https://angular-muvaqu.stackblitz.io/

Side note : If an error ever occurs and asks you to add BrowserAnimationsModule, just import it in your app.module.ts:

import { BrowserAnimationsModule } from '@angular/platform-browser/animations';

@NgModule({
  imports: [ ..., BrowserAnimationsModule ],
  ...
})