text: 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
  }
  
  // requestAnimationFrame for Smart Animating http://goo.gl/sx5sts
  const requestAnimFrame = (function () {
    return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame ||
        function (callback) {
          window.setTimeout(callback, 1000 / 60)
        }
  })();
  
  /**
   * Because it's so fucking difficult to detect the scrolling element, just move them all
   * @param {number} amount
   */
  function move(amount) {
    document.documentElement.scrollTop = amount
    document.body.parentNode.scrollTop = amount
    document.body.scrollTop = amount
  }
  
  function position() {
    return document.documentElement.scrollTop || document.body.parentNode.scrollTop || document.body.scrollTop
  }
  
  /**
   * @param {number} to
   * @param {number} duration
   * @param {Function} callback
   */
  export function scrollTo(to, duration, callback) {
    const start = position()
    const change = to - start
    const increment = 20
    let currentTime = 0
    duration = (typeof (duration) === 'undefined') ? 500 : duration
    const animateScroll = function () {
      // increment the time
      currentTime += increment
      // find the value with the quadratic in-out easing function
      const val = Math.easeInOutQuad(currentTime, start, change, duration);
      // move the document.body
      move(val)
      // do the animation unless its over
      if (currentTime < duration) {
        requestAnimFrame(animateScroll)
      } else {
        if (callback && typeof (callback) === 'function') {
          // the animation is done so lets callback
          callback()
        }
      }
    };
    animateScroll()
  }
  