requestTimeout.js

// Drop in replace functions for setTimeout() & setInterval() that 
// make use of requestAnimationFrame() for performance where available
// http://www.joelambert.co.uk

// Copyright 2011, Joe Lambert.
// Free to use under the MIT license.
// http://www.opensource.org/licenses/mit-license.php

// requestAnimationFrame() shim by Paul Irish
// http://paulirish.com/2011/requestanimationframe-for-smart-animating/
window.requestAnimFrame = (function() {
    return  window.requestAnimationFrame       || 
            window.webkitRequestAnimationFrame || 
            window.mozRequestAnimationFrame    || 
            window.oRequestAnimationFrame      || 
            window.msRequestAnimationFrame     || 
            function(/* function */ callback, /* DOMElement */ element){
                window.setTimeout(callback, 1000 / 60);
            };
})();

/**
 * Behaves the same as setTimeout except uses requestAnimationFrame() where possible for better performance
 * @param {function} fn The callback function
 * @param {int} delay The delay in milliseconds
 */

window.requestTimeout = function(fn, delay) {
    if( !window.requestAnimationFrame       && 
        !window.webkitRequestAnimationFrame && 
        !(window.mozRequestAnimationFrame && window.mozCancelRequestAnimationFrame) && // Firefox 5 ships without cancel support
        !window.oRequestAnimationFrame      && 
        !window.msRequestAnimationFrame)
            return window.setTimeout(fn, delay);
            
    var start = new Date().getTime(),
        handle = new Object();
        
    function loop(){
        var current = new Date().getTime(),
            delta = current - start;
            
        delta >= delay ? fn.call() : handle.value = requestAnimFrame(loop);
    };
    
    handle.value = requestAnimFrame(loop);
    return handle;
};

/**
 * Behaves the same as clearTimeout except uses cancelRequestAnimationFrame() where possible for better performance
 * @param {int|object} fn The callback function
 */
window.clearRequestTimeout = function(handle) {
    window.cancelAnimationFrame ? window.cancelAnimationFrame(handle.value) :
    window.webkitCancelAnimationFrame ? window.webkitCancelAnimationFrame(handle.value) :
    window.webkitCancelRequestAnimationFrame ? window.webkitCancelRequestAnimationFrame(handle.value) : /* Support for legacy API */
    window.mozCancelRequestAnimationFrame ? window.mozCancelRequestAnimationFrame(handle.value) :
    window.oCancelRequestAnimationFrame ? window.oCancelRequestAnimationFrame(handle.value) :
    window.msCancelRequestAnimationFrame ? window.msCancelRequestAnimationFrame(handle.value) :
    clearTimeout(handle);
};