requestAnimationFrame polyfill

requestAnimationFrame.js

// Adapted from https://gist.github.com/paulirish/1579671 which derived from 
// http://paulirish.com/2011/requestanimationframe-for-smart-animating/
// http://my.opera.com/emoller/blog/2011/12/20/requestanimationframe-for-smart-er-animating

// requestAnimationFrame polyfill by Erik Möller.
// Fixes from Paul Irish, Tino Zijdel, Andrew Mao, Klemen Slavič, Darius Bacon

// MIT license

(function() {
    'use strict';

    var vendors = ['webkit', 'moz'];
    for (var i = 0; i < vendors.length && !window.requestAnimationFrame; ++i) {
        var vp = vendors[i];
        window.requestAnimationFrame = window[vp+'RequestAnimationFrame'];
        window.cancelAnimationFrame = (window[vp+'CancelAnimationFrame']
        || window[vp+'CancelRequestAnimationFrame']);
    }
    if (/iP(ad|hone|od).*OS 6/.test(window.navigator.userAgent) // iOS6 is buggy
        || !window.requestAnimationFrame || !window.cancelAnimationFrame) {
        var lastTime = 0;
        window.requestAnimationFrame = function(callback) {
            var now = +new Date;
            var nextTime = Math.max(lastTime + 16, now);
            return setTimeout(function() { callback(lastTime = nextTime); },
                nextTime - now);
        };
        window.cancelAnimationFrame = clearTimeout;
    }

    var hasPerformance = !!(window.performance && window.performance.now);
    // Add new wrapper for browsers that don't have performance
    if (!hasPerformance) {
        // Store reference to existing rAF and initial startTime
        var rAF = window.requestAnimationFrame,
            startTime = +new Date;

        // Override window rAF to include wrapped callback
        window.requestAnimationFrame = function (callback, element) {
            // Wrap the given callback to pass in performance timestamp
            var wrapped = function (timestamp) {
                // Get performance-style timestamp
                var performanceTimestamp = (timestamp < 1e12)
                    ? timestamp
                    : timestamp - startTime;

                return callback(performanceTimestamp);
            };

            // Call original rAF with wrapped callback
            rAF(wrapped, element);
        }
    }
}());