This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.

The Animation.startTime property of the Animation interface is a double-precision floating-point value which indicates the scheduled time when an animation's playback should begin. 

An animation’s start time is the time value of its DocumentTimeline when its target KeyframeEffect is scheduled to begin playback. An animation’s start time is initially unresolved (meaning that it's null because it has no value).

Syntax

var animationStartedWhen = Animation.startTime;

Animation.startTime = newStartTime;

Value

A floating-point number representing the current time in milliseconds, or null if no time is set. You can read this value to determine what the start time is currently set at, and you can change this value to make the animation start at a different time.

Examples

In the Running on Web Animations API example, the we can sync all new animated cats by giving them all the same startTime as the original running cat:

var catRunning = document.getElementById ("withWAAPI").animate(keyframes, timing);

/* A function that makes new cats. */
function addCat(){
  var newCat = document.createElement("div");
  newCat.classList.add("cat");
  return newCat;
}

/* This is the function that adds a cat to the WAAPI column */
function animateNewCatWithWAAPI() {
  // make a new cat
  var newCat = addCat();

  // animate said cat with the WAAPI's "animate" function
  var newAnimationPlayer = newCat.animate(keyframes, timing);

  // set the animation's start time to be the same as the original .cat#withWAAPI
  newAnimationPlayer.startTime = catRunning.startTime;

  // Add the cat to the pile.
  WAAPICats.appendChild(newCat);
}

Specifications

Specification Status Comment
Web Animations
The definition of 'Animation.startTime' in that specification.
Working Draft Editor's draft.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 39.0 48 (48)[1] No support No support No support
Feature Android Android Webview Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile Chrome for Android
Basic support No support 39.0 48.0 (48)[1] No support No support No support 39.0

[1] The Web Animations API is only enabled by default in Firefox Developer Edition and Nightly builds. You can enable it in beta and release builds by setting the preference dom.animations-api.core.enabled to true, and can disable it in any Firefox version by setting this preference to false.

See also

Document Tags and Contributors

 Last updated by: Sheppy,