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Ben Nadel at CFUNITED 2008 (Washington, D.C.) with: Peter Bell
Ben Nadel at CFUNITED 2008 (Washington, D.C.) with: Peter Bell ( @peterbell )

Automatic Property Calculation Support With Animations In Angular 2 RC 6

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One of the cool things about the Web Animations support in Angular 2 RC 6 is that you can use the "*" (wildcard) to reference the "runtime value" of a given property in either the source or destination styles of a transition. As I've been playing around with this feature, however, I've discovered that the support for this varies from browser to browser; and, also depends on whether or not you're using the Web Animations polyfill. So, moral of the story - be sure to test your animations and automatic property calculations across browsers.

Run this demo in my JavaScript Demos project on GitHub.

To demonstrate, I have a box that I can transition to and from the "void" state. In these transitions, I try to make use of:

  • width: "*"
  • height: "*"
  • borderRadius: "*"

In Chrome - which has native Web Animations support - and Sarafi - which uses the Web Animations polyfill - all three of these automatic property calculations work fine. In Firefox, however - which has native Web Animations support - height and width work but the borderRadius throws an error:

Animation to or from an underlying value is not yet supported.

I don't know if there's a list somewhere of the supported properties - these are just the few that I've tried to use in my research. Here's the demo code:

// Import the core angular services.
import { animate } from "@angular/core";
import { Component } from "@angular/core";
import { state } from "@angular/core";
import { style } from "@angular/core";
import { transition } from "@angular/core";
import { trigger } from "@angular/core";

@Component({
	selector: "my-app",
	animations: [
		trigger(
			"boxAnimation",
			[
				// When transitioning to and from a given state, we can SOMETIMES use
				// the "*" to leverage whatever the existing runtime value is (or should
				// be) for the given property. Support for this depends on the browser.
				// For example, in Chrome, we can use borderRadius:"*"; but, in Firefox,
				// it will throw the error:
				// --
				// Animation to or from an underlying value is not yet supported.
				// --
				// Both Chrome and Firefox support width:"*" and height:"*".
				transition(
					"void => *",
					[
						style({
							height: 0,
							width: 0
						}),
						animate(
							"1000ms ease-in-out",
							style({
								height: "*",
								width: "*"
							})
						)
					]
				),
				transition(
					"* => void",
					[
						style({
							borderRadius: "*",
							height: "*",
							width: "*"
						}),
						animate(
							"1000ms ease-in-out",
							style({
								borderRadius: 0,
								height: 0,
								width: 0
							})
						)
					]
				)
			]
		)
	],
	template:
	`
		<p>
			<a (click)="toggleBox()">Toggle Box</a>
		</p>

		<div *ngIf="isShowingBox" @boxAnimation class="box">
			<br />
		</div>
	`
})
export class AppComponent {

	public isShowingBox: boolean;


	// I initialize the component.
	constructor() {

		this.isShowingBox = false;

	}


	// ---
	// PUBLIC METHODS.
	// ---


	// I show or hide the box depending on the current state.
	public toggleBox() : void {

		this.isShowingBox = ! this.isShowingBox;

	}

}

When executing the "enter" transition, I'm only using "height" and "width"; so, these should work in all the browsers. But, when executing the "leave" transition, I'm also using "borderRadius", which will break in Firefox:

Automatic property calculation support in Angular 2 RC 6 web animations need to be tested across browsers.

The automatic property calculation feature in Angular 2 RC 6 is very awesome and is something that I'm excited to dig into more. The take-away of this post is simply that browser support varies and that you need to remember to test your animations across browsers - even when the browser has native Web Animations support.

Want to use code from this post? Check out the license.

Reader Comments

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Ben Nadel