function scrollTo(Y, duration, easingFunction, callback) { var start = Date.now(), elem = document.documentElement.scrollTop?document.documentElement:document.body, from = elem.scrollTop; 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(time); elem.scrollTop = (easedT * (Y - from)) + from; if(time < 1) requestAnimationFrame(scroll); else if(callback) callback(); } requestAnimationFrame(scroll) } /* bits and bytes of the scrollTo function inspired by the works of Benjamin DeCock */ /* * Easing Functions - inspired from http://gizma.com/easing/ * only considering the t value for the range [0, 1] => [0, 1] */ 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<.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<.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<.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<.5 ? 16*t*t*t*t*t : 1+16*(--t)*t*t*t*t } } /* Add the following to you main js file // 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 and Tino Zijdel (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); }; }()); */