window.requestAnimationFrame()

The window.requestAnimationFrame() method tells the browser that you wish to perform an animation and requests that the browser call a specified function to update an animation before the next repaint. The method takes a callback as an argument to be invoked before the repaint.

You should call this method whenever you're ready to update your animation onscreen. This will request that your animation function be called before the browser performs the next repaint. The number of callbacks is usually 60 times per second, but will generally match the display refresh rate in most web browsers as per W3C recommendation. requestAnimationFrame() calls are paused in most browsers when running in background tabs or hidden <iframe>s in order to improve performance and battery life.

The callback method is passed a single argument, a DOMHighResTimeStamp, which indicates the current time when callbacks queued by requestAnimationFrame() begin to fire. Multiple callbacks in a single frame, therefore, each receive the same timestamp even though time has passed during the computation of every previous callback's workload. This timestamp is a decimal number, in milliseconds, but with a minimal precision of 1ms (1000 µs).

Syntax

window.requestAnimationFrame(callback);

Parameters

callback

A parameter specifying a function to call when it's time to update your animation for the next repaint. The callback has one single argument, a DOMHighResTimeStamp, which indicates the current time (the time returned from performance.now() ) for when requestAnimationFrame() starts to fire callbacks.

Return value

A long integer value, the request id, that uniquely identifies the entry in the callback list. This is a non-zero value, but you may not make any other assumptions about its value. You can pass this value to window.cancelAnimationFrame() to cancel the refresh callback request.

Example

var start = null;
var element = document.getElementById('SomeElementYouWantToAnimate');
element.style.position = 'absolute';

function step(timestamp) {
  if (!start) start = timestamp;
  var progress = timestamp - start;
  element.style.left = Math.min(progress / 10, 200) + 'px';
  if (progress < 2000) {
    window.requestAnimationFrame(step);
  }
}

window.requestAnimationFrame(step);

Specification

Browser compatibility

See also

• Window.mozAnimationStartTime
• Window.cancelAnimationFrame()
• mozRequestAnimationFrame - Blog post
• requestAnimationFrame for smart animating - Blog post
• Animating with javascript: from setInterval to requestAnimationFrame - Blog post
• Using PC Hardware more efficiently in HTML5: New Web Performance APIs, Part 1 - Blog post
• TestUFO: Test your web browser for requestAnimationFrame() Timing Deviations
• Paul Irish: requestAnimationFrame API: now with sub-millisecond precision