There used to be just one way to do a timed loop in JavaScript: setInterval() . If you needed to repeat something pretty fast (but not as-fast-as-absolutely-possible like a for loop), you’d use that. For the purposes of animation, the goal is sixty “frames” per second to appear smooth, so you’d run a loop like this:

setInterval(function() { // animiate something }, 1000/60);

There is a better alternative to this now. Paul Irish introduced requestAnimationFrame over two years ago. I don’t have a whole lot to add to it, I just had never actually used it before and now I have so I thought I’d help spread the word and write about its basic usage.

Why better?

As Paul explained:

The browser can optimize it, so animations will be smoother

Animations in inactive tabs will stop, allowing the CPU to chill

More battery-friendly

The Simplest Possible Example

function repeatOften() { // Do whatever requestAnimationFrame(repeatOften); } requestAnimationFrame(repeatOften);

Call it once to kick it off, and your function recursively calls itself.

Start and Stop

requestAnimationFrame returns an ID you can use to cancel it, just like setTimeout or setInterval does. jQuery used here only to demonstrate a simple animation and bind events.

var globalID; function repeatOften() { $("<div />").appendTo("body"); globalID = requestAnimationFrame(repeatOften); } $("#start").on("click", function() { globalID = requestAnimationFrame(repeatOften); }); $("#stop").on("click", function() { cancelAnimationFrame(globalID); });

Example of this:

Browser Support

See the Can I Use… tables.

The only notable problems are IE 9-, iOS 5-, and Android. But not actually a problem, because:

Polyfill

Like many fancy web features, it’s nice to use it when available and fallback to something that works when you can’t. Probably best just to refer to this Gist. Literally just include that chunk anywhere before you use requestAnimationFrame or cancelAnimationFrame .

Using this, you’ll be able to use requestAnimationFrame in literally any browser.

Slightly More Complex Example

I learned about this while making a dumb little demo to learn canvas better:

See the Pen Super Simple requestAnimationFrame Thing by Chris Coyier (@chriscoyier) on CodePen.

What would actually be more complex is several animations running at once using this (that still falls back OK). Feel free to link some of that goodness up in the comments if you know of examples.