scroll to snippet without framework dependency using requestAnimationFrame

scroll-to.js

;(function(window, document, undefined) {
    // rAF polyfill
    (function() {
        var lastTime = 0;
        var vendors = ['ms', 'moz', 'webkit', 'o'];
        for(var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) {
            window.requestAnimationFrame = window[vendors[x]+'RequestAnimationFrame'];
            window.cancelAnimationFrame = window[vendors[x]+'CancelAnimationFrame'] || window[vendors[x]+'CancelRequestAnimationFrame'];
        }

        if (!window.requestAnimationFrame) {
            window.requestAnimationFrame = function(callback, element) {
                var currTime = new Date().getTime();
                var timeToCall = Math.max(0, 16 - (currTime - lastTime));
                var id = window.setTimeout(function() { callback(currTime + timeToCall); },
                  timeToCall);
                lastTime = currTime + timeToCall;
                return id;
            };
        }

        if (!window.cancelAnimationFrame) {
            window.cancelAnimationFrame = function(id) {
                clearTimeout(id);
            };
        }
    }());

    var _isIE = function (obj) {
        return navigator.userAgent.toLowerCase().indexOf('msie') !== -1 || navigator.userAgent.toLowerCase().indexOf('trident') !== -1;
    };

    var _isFirefox = function(){
        return typeof InstallTrigger !== 'undefined';   
    };

    var easing = {
        // no easing, no acceleration
        linear: function (t) { return t; },
        // accelerating from zero velocity
        easeInQuad: function (t) { return t*t; },
        // decelerating to zero velocity
        easeOutQuad: function (t) { return t*(2-t); },
        // acceleration until halfway, then deceleration
        easeInOutQuad: function (t) { return t<0.5 ? 2*t*t : -1+(4-2*t)*t; },
        // accelerating from zero velocity
        easeInCubic: function (t) { return t*t*t; },
        // decelerating to zero velocity
        easeOutCubic: function (t) { return (--t)*t*t+1; },
        // acceleration until halfway, then deceleration
        easeInOutCubic: function (t) { return t<0.5 ? 4*t*t*t : (t-1)*(2*t-2)*(2*t-2)+1; },
        // accelerating from zero velocity
        easeInQuart: function (t) { return t*t*t*t; },
        // decelerating to zero velocity
        easeOutQuart: function (t) { return 1-(--t)*t*t*t; },
        // acceleration until halfway, then deceleration
        easeInOutQuart: function (t) { return t<0.5 ? 8*t*t*t*t : 1-8*(--t)*t*t*t; },
        // accelerating from zero velocity
        easeInQuint: function (t) { return t*t*t*t*t; },
        // decelerating to zero velocity
        easeOutQuint: function (t) { return 1+(--t)*t*t*t*t; },
        // acceleration until halfway, then deceleration
        easeInOutQuint: function (t) { return t<0.5 ? 16*t*t*t*t*t : 1+16*(--t)*t*t*t*t; }
    };

    function scrollTo(Y, duration, easingFunction, callback) {

        var start = Date.now(),
            elem = document.documentElement.scrollTop ? document.documentElement : document.body,
            from = elem.scrollTop;

        if (_isIE()) {
            elem = document.documentElement;
        }

        if (_isFirefox()) {
            elem = document.documentElement;
        }

        callback = typeof callback === 'function' ? callback : noop;

        if(from === Y) {
            callback();
            return; /* Prevent scrolling to the Y point if already there */
        }

        function min(a,b) {
            return a<b?a:b;
        }

        function scroll(timestamp) {

            var currentTime = Date.now(),
                time = min(1, ((currentTime - start) / duration)),
                easedT = easingFunction !== undefined ? easingFunction(time) : time;

            elem.scrollTop = (easedT * (Y - from)) + from;

            if(time < 1) {
                requestAnimationFrame(scroll);
            } else {
                if(callback) {
                    callback();
                }
            }
        }

        requestAnimationFrame(scroll);
    };

    window.scrollTo = scrollTo;
})(window, document);

The script logic was not developed by me, but I could not find the place where I got the code.