Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.
Non-standard: This feature is not standardized. We do not recommend using non-standard features in production, as they have limited browser support, and may change or be removed. However, they can be a suitable alternative in specific cases where no standard option exists.
This method is used to break up long running operations and run a callback function immediately after the browser has completed other operations such as events and display updates.
This method can be used instead of the setTimeout(fn, 0) method to execute heavy operations.
The feature can be emulated in a few different ways:
postMessage() can be used to trigger an immediate but yielding callback.
MessageChannel can be used reliably inside of Web Workers whereas the
semantics of postMessage mean it cannot be used there.
setTimeout(fn, 0)can potentially be used, however as it is clamped to 4ms for timers nested more than 5 levels deep per the HTML spec, it does not make for a suitable polyfill for the natural immediacy of setImmediate.
