requestIdleCallback
polyfill/shim
This is a polyfill/shim for the requestIdleCallback
and cancelIdleCallback
API. Also fixes early API implementation.
For more information see the Cooperative Scheduling of Background Tasks Draft.
Installation
Include the "index.js" in your website and use requestIdleCallback
and cancelIdleCallback
according to the specification.
How it works
requestIdleCallback
can't be really polyfilled. Therefore requestIdleCallback
basically includes a throttle like function, that uses some heuristics to detect a) long running frames and b) user input as also DOM mutations to adapt accordingly. requestIdleCallback
also tries to get the time right after a frame commit. The deadline.timeRemaining()
either starts with 7ms or with 22ms for the first scheduled callback.
If multiple functions are scheduled with the requestIdleCallback
shim for the same idle time, the shim makes sure to split those functions as soon as timeRemaining()
is exceeded.
Usage
If you have a fast or a non-splittable task:
;
In case you have a heavy and splittable task you can use efficient script yielding technique:
;
Reading vs writing layout: requestIdleCallback
is mainly for layout neutral or layout reading/measuring tasks. In case you want to write layout/manipulate the DOM consider using requestAnimationFrame
instead.
Of course requestIdleCallback
can also be combined with requestAnimationFrame
:
;