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.
timeout
option is strongly recommended for required work, as otherwise it's possible multiple seconds will elapse before the callback is fired.Syntax
var handle = 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
: Iftimeout
is specified and has a positive value, and the callback has not already been called by the time timeout milliseconds have passed, the callback will be called during the next idle period, even if doing so risks causing a negative performance impact.
Example
See our complete example in the article Cooperative Scheduling of Background Tasks API.
Specifications
Specification | Status | Comment |
---|---|---|
Cooperative Scheduling of Background Tasks | Proposed Recommendation | Initial definition. |
Browser compatibility
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
requestIdleCallback | Chrome Full support 47 | Edge Full support 79 | Firefox
Full support
55
| IE No support No | Opera Full support 34 | Safari No support No | WebView Android Full support 47 | Chrome Android Full support 47 | Firefox Android
Full support
55
| Opera Android Full support 34 | Safari iOS No support No | Samsung Internet Android Full support 5.0 |
Legend
- Full support
- Full support
- No support
- No support
- Experimental. Expect behavior to change in the future.
- Experimental. Expect behavior to change in the future.
- See implementation notes.
- See implementation notes.