window.requestIdleCallback()

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The window.requestIdleCallback() method queues a function to be called during a browser's idle periods. This enables developers to perform background and low priority work on the main event loop, without impacting latency-critical events such as animation and input response. Functions are generally called in first-in-first-out order; however, callbacks which have a timeout specified may be called out-of-order if necessary in order to run them before the timeout elapses.

You can call requestIdleCallback() within an idle callback function to schedule another callback to take place no sooner than the next pass through the event loop.

Note: A timeout option is strongly recommended for required work, as otherwise it's possible multiple seconds will elapse before the callback is fired.

Syntax

window.requestIdleCallback(callback);
window.requestIdleCallback(callback, options);

Return value

An ID which can be used to cancel the callback by passing it into the window.cancelIdleCallback() method.

Parameters

callback

A reference to a function that should be called in the near future, when the event loop is idle. The callback function is passed an IdleDeadline object describing the amount of time available and whether or not the callback has been run because the timeout period expired.

options Optional

Contains optional configuration parameters. Currently only one property is defined:

  • timeout: If the number of milliseconds represented by this parameter has elapsed and the callback has not already been called, then a task to execute the callback is queued in the event loop (even if doing so risks causing a negative performance impact). timeout must be a positive value or it is ignored.

Example

See our complete example in the article Cooperative Scheduling of Background Tasks API.

Specifications

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
requestIdleCallback
47
79
55
No
34
No
47
47
55
34
No
5.0

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/Window/requestIdleCallback