async.js

/*! Cross-browser-compatible async
 *
 * I took Mathias' setZeroTimeout and changed it to async, based on http://fitzgeraldnick.com/weblog/35/. Some style changes (varible names, show logic first).
 *
 * I took the original setZeroTimeout and made it cross-browser-compatible, using setTimeout(fn, 0) as a fallback in case postMessage is not supported.
 * Mathias Bynens <http://mathiasbynens.be/>
 * See <http://mathiasbynens.be/notes/settimeout-onload>
 *
 * Copyright statement below:
 *
 * See <http://dbaron.org/log/20100309-faster-timeouts>
 * By L. David Baron <dbaron@dbaron.org>, 2010-03-07, 2010-03-09
 * Released under the following license:
 *
 * Copyright (c) 2010, The Mozilla Foundation
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * - Redistributions of source code must retain the above copyright
 * - notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 * - notice, this list of conditions and the following disclaimer in
 * - the documentation and/or other materials provided with the
 * - distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

// BEGIN implementation of async

// Only add async to the window object, and hide everything else in a closure.
(function() {

    var timeouts = [],
        message_name = 'async-message',
        outer = window;

    if (outer.postMessage) {
        if (outer.addEventListener) {
            outer.addEventListener('message', handleMessage, true);
        } else if (outer.attachEvent) {
            outer.attachEvent('onmessage', handleMessage);
        }
        outer.async = postMessage;
    } else {
        outer.async = async;
    }

    // Like setTimeout, but only takes a function argument.  There's
    // no time argument (always zero) and no arguments (you have to
    // use a closure).
    function postMessage(fn) {
        timeouts.push(fn);
        outer.postMessage(message_name, '*');
    }

    function async(fn) {
        outer.setTimeout(fn, 0);
    }

    function handleMessage(event) {
        if (event.source == outer && event.data == message_name) {
            if (event.stopPropagation) {
                event.stopPropagation();
            }
            if (timeouts.length) {
                (timeouts.shift())();
            }
        }
    }

}());

// END implementation of async