scrollTo.js

/*
 *
 * Works with elements or jquery
 *
 * scrollTo(element, duration, offset);
 *
 * Update 'scroller' variable with custom scrolling element if not document.body
 *
 */

define([
    'gsap'
], function() {
    var dummy = document.createElement('div');
    var isWebkit = 'WebkitAppearance' in document.documentElement.style;
    var scroller = isWebkit ? document.body : document.documentElement;

    return function( element, duration, offset ){
        var minDuration = 0.2;
        var offset = offset || 0;
        var element = element instanceof jQuery ? element.get(0) : element;
        var distance = Math.abs( element.offsetTop - scroller.scrollTop + offset );
        var duration = duration || (minDuration + distance / 3000).toFixed(2);

        TweenLite.set(dummy, { x: scroller.scrollTop });
        TweenLite.to(dummy, duration, {
            x: element.offsetTop + offset, 
            ease: Power1.easeInOut, 
            onUpdate: function() {
                scroller.scrollTop = (dummy._gsTransform.x).toFixed(2);
            }
        });
    }
})