better requestAnimationFrame management

gistfile1.js

var now = Date.now || function () {
        return new Date().getTime();
    },
    uniqueId = (function () {
        var cache = {};
        return function (prefix, isInt) {
            var val;
            if (!prefix) {
                prefix = '';
            }
            prefix += '';
            val = cache[prefix];
            if (!val) {
                val = cache[prefix] = 0;
            }
            cache[prefix]++;
            if (!isInt) {
                val = prefix + val;
            }
            return val;
        };
    }()),
    AF = (function () {
        var currentlyRunning, win = window,
            x = 0,
            lastTime = 0,
            vendors = 'ms moz webkit o'.split(' '),
            fnList = [],
            addList = [],
            removeList = [],
            run = function () {
                var i = 0,
                    listLen = fnList.length,
                    removeLater = [];
                fnList = fnList.concat(addList);
                addList = [];
                for (; i < listLen; i++) {
                    fnObj = fnList[i];
                    if (removeList.indexOf(fnObj.id) === -1) {
                        currentlyRunning = fnObj;
                        fnObj.fn(now());
                    }
                }
                currentlyRunning = void 0;
                for (i = 0; i < removeList.length; i++) {
                    fnList.splice(fnList.indexOf(removeList[i]), 1);
                }
                removeList = [];
                if (fnList.length) {
                    win.requestAnimationFrame(run);
                }
            };
        for (; x < getLength(vendors) && !win.requestAnimationFrame; ++x) {
            win.requestAnimationFrame = win[vendors[x] + 'RequestAnimationFrame'];
            win.cancelAnimationFrame = win[vendors[x] + 'CancelAnimationFrame'] || win[vendors[x] + 'CancelRequestAnimationFrame'];
        }
        if (!win.requestAnimationFrame) {
            win.requestAnimationFrame = function (callback, element) {
                var currTime = new Date().getTime(),
                    timeToCall = Math.max(0, 16 - (currTime - lastTime)),
                    id = window.setTimeout(function () {
                        callback(currTime + timeToCall);
                    }, timeToCall);
                lastTime = currTime + timeToCall;
                return id;
            };
        }
        if (!win.cancelAnimationFrame) {
            win.cancelAnimationFrame = function (id) {
                clearTimeout(id);
            };
        }
        return {
            cancel: function (id) {
                removeList.push(id);
            },
            remove: function () {
                removeList.push(currentlyRunning.id);
            },
            request: function (fn) {
                var id = uuid();
                if (typeof fn === 'function') {
                    if (!fnList.length) {
                        win.requestAnimationFrame(run);
                    }
                    addList.push({
                        fn: fn,
                        id: id
                    });
                    return id;
                }
            }
        };
    }());