alReady.js is a terse, embeddable, and cross-browser DOMContentLoaded implementation. It aims to hit a sweet spot in the tradeoff between size and embeddability on one side, and browser compatibility on the other.
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Terse: alReady.js contains just over 200 bytes after closure minification and gzipping.
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Embeddable: alReady.js has no dependencies, and can be dropped as-is into your own code or library.
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Cross-browser: alReady.js will work in any web browser.
alReady.js was inspired by this tweet from Twitter's Dustin Diaz, which started a mad round of code-golfing from a bunch of folks that follow Dustin, ending in this genius 60-byte implementation from Tobie Langel:
function r(f){setTimeout(/in/(document.readyState)?f:r,9,f)}
Unfortunately, a bunch of things prevent this from being usable on the real web, including the fact that Firefox 3.5 and earlier has no document.readyState property to check, and that Internet Explorer doesn't support additional arguments in setTimeout (in IE, the third argument specifies -- get this -- the name of the language used: JScript, VBScript, or JavaScript).
Dustin blogged about his end solution, working it into his $script.js library, but I wanted something more embeddable, so I went in a different direction, trying backoff polling and other cross-browser methods.
Eventually, John-David Dalton pointed me to Diego Perini's implementation, from which the current version is largely inspired. The biggest difference is that alReady.js is much smaller at just over 200 gzipped bytes, and does not optimize on edge cases for soon-to-be-negligible versions of IE.
callback is guaranteed to be called once and only once. Use alReady.call( window, callback ) to specify the window of the document to be checked.
If the document has already loaded, callback is called immediately. Otherwise, callback is bound to the window's load event and document's DOMContentLoaded and readystatechange events, and is called when the first one occurs.
Send any questions or comments here.
Copyright (c) 2011 Jed Schmidt. See LICENSE.txt for details.