scrollTo animate

scrollTo.js

//scrollTop
  function scrollTo(element, to, duration) {
    var start = element.scrollTop,
        change = to - start,
        currentTime = 0,
        increment = 20;

    var animateScroll = function(){
        currentTime += increment;
        var val = Math.easeInOutQuad(currentTime, start, change, duration);
        element.scrollTop = val;
        if(currentTime < duration) {
            setTimeout(animateScroll, increment);
        }
    };
    animateScroll();
  }

  //t = current time
  //b = start value
  //c = change in value
  //d = duration
  Math.easeInOutQuad = function (t, b, c, d) {
      t /= d/2;
      if (t < 1) return c/2*t*t + b;
      t--;
      return -c/2 * (t*(t-2) - 1) + b;
  }