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.
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
BCD tables only load in the browser