| # immediate [](https://travis-ci.org/calvinmetcalf/immediate) |
|
|
| ``` |
| npm install immediate --save |
| ``` |
|
|
| then |
|
|
| ```js |
| var immediate = require("immediate"); |
| |
| immediate(function () { |
| // this will run soon |
| }); |
| |
| immediate(function (arg1, arg2) { |
| // get your args like in iojs |
| }, thing1, thing2); |
| ``` |
|
|
| ## Introduction |
|
|
| **immediate** is a microtask library, decended from [NobleJS's setImmediate](https://github.com/NobleJS/setImmediate), but including ideas from [Cujo's When](https://github.com/cujojs/when) and [RSVP][RSVP]. |
|
|
| immediate takes the tricks from setImmedate and RSVP and combines them with the schedualer inspired (vaugly) by whens. |
|
|
| Note versions 2.6.5 and earlier were strictly speaking a 'macrotask' library not a microtask one, [see this for the difference](https://github.com/YuzuJS/setImmediate#macrotasks-and-microtasks), if you need a macrotask library, [I got you covered](https://github.com/calvinmetcalf/macrotask). |
|
|
| Several new features were added in versions 3.1.0 and 3.2.0 to maintain parity with |
| process.nextTick, but the 3.0.x series is still being kept up to date if you just need |
| the small barebones version. |
|
|
|
|
| ## The Tricks |
|
|
| ### `process.nextTick` |
|
|
| Note that we check for *actual* Node.js environments, not emulated ones like those produced by browserify or similar. |
|
|
| ### `MutationObserver` |
|
|
| This is what [RSVP][RSVP] uses, it's very fast, details on [MDN](https://developer.mozilla.org/en-US/docs/Web/API/MutationObserver). |
|
|
|
|
| ### `MessageChannel` |
|
|
| Unfortunately, `postMessage` has completely different semantics inside web workers, and so cannot be used there. So we |
| turn to [`MessageChannel`][MessageChannel], which has worse browser support, but does work inside a web worker. |
|
|
| ### `<script> onreadystatechange` |
|
|
| For our last trick, we pull something out to make things fast in Internet Explorer versions 6 through 8: namely, |
| creating a `<script>` element and firing our calls in its `onreadystatechange` event. This does execute in a future |
| turn of the event loop, and is also faster than `setTimeout(…, 0)`, so hey, why not? |
|
|
| ## Tricks we don't use |
|
|
| ### `setImmediate` |
| We avoid this process.nextTick in node is better suited to our needs and in Internet Explorer 10 there is a broken version of setImmediate we avoid using this. |
|
|
|
|
| In Node.js, do |
|
|
| ``` |
| npm install immediate |
| ``` |
|
|
| then |
|
|
| ```js |
| var immediate = require("immediate"); |
| ``` |
|
|
|
|
| ## Reference and Reading |
|
|
| * [Efficient Script Yielding W3C Editor's Draft][spec] |
| * [W3C mailing list post introducing the specification][list-post] |
| * [IE Test Drive demo][ie-demo] |
| * [Introductory blog post by Nicholas C. Zakas][ncz] |
| * I wrote a couple blog pots on this, [part 1][my-blog-1] and [part 2][my-blog-2] |
|
|
| [RSVP]: https://github.com/tildeio/rsvp.js |
| [spec]: https://dvcs.w3.org/hg/webperf/raw-file/tip/specs/setImmediate/Overview.html |
| [list-post]: http://lists.w3.org/Archives/Public/public-web-perf/2011Jun/0100.html |
| [ie-demo]: http://ie.microsoft.com/testdrive/Performance/setImmediateSorting/Default.html |
| [ncz]: http://www.nczonline.net/blog/2011/09/19/script-yielding-with-setimmediate/ |
| [nextTick]: http://nodejs.org/docs/v0.8.16/api/process.html#process_process_nexttick_callback |
| [postMessage]: http://www.whatwg.org/specs/web-apps/current-work/multipage/web-messaging.html#posting-messages |
| [MessageChannel]: http://www.whatwg.org/specs/web-apps/current-work/multipage/web-messaging.html#channel-messaging |
| [cross-browser-demo]: http://calvinmetcalf.github.io/setImmediate-shim-demo |
| [my-blog-1]:http://calvinmetcalf.com/post/61672207151/setimmediate-etc |
| [my-blog-2]:http://calvinmetcalf.com/post/61761231881/javascript-schedulers |
|
|
