未捕获的ReferenceError：未定义目标（SmoothScroll）

Question

我的用于平滑滚动的JS代码返回了未定义目标的错误，我不确定100％这意味着什么，所以我无法自己修复该错误。

错误：

未捕获的ReferenceError：未定义目标

我需要定义什么才能使其正常工作？

工作示例：http://oxfordlocks.co.uk/Explore/beast.html

JS：

  function init(){
    new SmoothScroll(document,30,24)
  }

  function SmoothScroll(body, speed, smooth) {
    if (target === document)
      target = (document.scrollingElement 
                || document.documentElement 
                || document.body.parentNode 
                || document.body) // cross browser support for document scrolling

    var moving = false
    var pos = target.scrollTop
    var frame = target === document.body 
                && document.documentElement 
                ? document.documentElement 
                : target // safari is the new IE

    target.addEventListener('mousewheel', scrolled, { passive: false })
    target.addEventListener('DOMMouseScroll', scrolled, { passive: false })

    function scrolled(e) {
      e.preventDefault(); // disable default scrolling

      var delta = normalizeWheelDelta(e)

      pos += -delta * speed
      pos = Math.max(0, Math.min(pos, target.scrollHeight - frame.clientHeight)) // limit scrolling

      if (!moving) update()
    }

    function normalizeWheelDelta(e){
      if(e.detail){
        if(e.wheelDelta)
          return e.wheelDelta/e.detail/40 * (e.detail>0 ? 1 : -1) // Opera
        else
          return -e.detail/3 // Firefox
      }else
        return e.wheelDelta/120 // IE,Safari,Chrome
    }

    function update() {
      moving = true

      var delta = (pos - target.scrollTop) / smooth

      target.scrollTop += delta

      if (Math.abs(delta) > 0.5)
        requestFrame(update)
      else
        moving = false
    }

    var requestFrame = function() { // requestAnimationFrame cross browser
      return (
        window.requestAnimationFrame ||
        window.webkitRequestAnimationFrame ||
        window.mozRequestAnimationFrame ||
        window.oRequestAnimationFrame ||
        window.msRequestAnimationFrame ||
        function(func) {
          window.setTimeout(func, 1000 / 50);
        }
      );
    }()
  }