This repository contains utility libraries for Web Animations, which is a new JavaScript API for driving animated content on the web.

For more information, see the specification, browser support, and polyfill.

The timeline library provides a manager of many Animation player instances, and is useful for scheduling and scrubbing a collection of animations and related callbacks.

It is supported natively on Chrome 39+, and requires the web-animations polyfill on other, modern browsers.

var timeline = new AnimationUtilTimeline();

var element = ...;
var steps = [{transform: 'translate(0)'}, {transform: 'translate(1000px)'}];

timeline.schedule(250, element, steps, 1500);
timeline.call(250 + 750, function() {
  console.info('half-way there!');
  timeline.playbackRate *= 2;

  // schedule a further animation, after the timeline has started.
  timeline.schedule(1500, otherElement, differentSteps, 1000);
});

The props library provides a helper to apply the final state of the passed animation as inline CSS properties.

It is supported natively on Chrome 39+, and requires the web-animations polyfill on other, modern browsers.

var element = ...;
var steps = [{transform: 'translate(0)'}, {transform: 'translate(1000px)'}];
var anim = element.animate(steps, 1000);
AnimationUtilApply(steps, element);

It also supports the advanced polyfill features in web-animations-next, such as KeyframeEffect, GroupEffect and SequenceEffect.

var effect = new KeyframeEffect(target, steps);
var group = new GroupEffect([effect, ...]);
var anim = document.timeline.play(group);
AnimationUtilApply(group);

Externs can be used inside the Closure Compiler to hint at functions provided outside a project's code base, such as third-party libraries or for upcoming APIs such as Web Animations. For more information, see Advanced Compilation and Externs.

The utility library provides two externs files that may be used in Closure. The externs.js defines basic features (matching web-animations), and the externs-next.js defines advanced features (matching web-animations-next). To use externs-next.js, you should include both externs files.

java -jar compiler.jar --compilation_level ADVANCED_OPTIMIZATIONS \
  --js yourcode.js web-animations-utils/externs*

These can be specified with --externs or just as source (as both files are annotated with @externs).