/**定于延时执行函数**/
 var timeFun = null;
 /**找到当前页面滚动到的锚点位置**/
 var findHref = function(){
  var $links = $('.link');
  var windowScrollTop = $(window).scrollTop();
  var maxDistance = 10000;
  var result = $links.eq(0);
  $.each($links,function(i,link){
   var curDistanceToTop = Math.abs($links.eq(i).offset().top - windowScrollTop);
   /**if(maxDistance > curDistanceToTop && ($links.eq(i).offset().top < (windowScrollTop + $(window).height()))){
    maxDistance = curDistanceToTop;
    result = $links.eq(i);
   } 这段代码相当于下面这一句代码，优秀的代码就应该拿来多学习！**/
   maxDistance > curDistanceToTop && $links.eq(i).offset().top < windowScrollTop + $(window).height() && (maxDistance = curDistanceToTop,result = $links.eq(i))
  });
  return result;
 };
 /***使用jQuery创建移动动画*/
 var move = function (dis) {
  var $arrow = $('.arrow');
  $arrow.animate({top:dis},'normal');
 }
 /**滚轮事件Handler**/
 var wheelHandler = function(e){
  clearTimeout(timeFun);
  timeFun = setTimeout(function(){
   var href = findHref();
   var index = href[0].id.substring(1);
   var dis = 30*(index-1)+10;
   move(dis);
  },600);
 };
 /***注册滚轮事件*/
 $('body').on('mousewheel',wheelHandler);