Team:USTC-Software/js/scroll

window.onload = function(){

   window.onscroll=function(){
       var top = document.documentElement.scrollTop || document.body.scrollTop;
       var menus = document.getElementById("menu").getElementsByTagName("a");
       var items=document.getElementById("content").getElementsByClassName("item");

       var currentId="";
       for(var i=0;i<items.length;i++){
           var _item=items[i];
           var _itemTop = _item.offsetTop;
           if(top>_itemTop-200){
               currentId=_item.id;
           }else{
               break;
           }
       }
       if(currentId!==""){
           //给正确的menu下的a元素class赋值
           for(var j=0;j<menus.length;j++){
               var _menu=menus[j];
               var _href=_menu.href.split("#");//因为只通过href获取的链接为一长串链接，需要通过#分成数组
               if(_href[_href.length-1]!==currentId){
                   _menu.className = "";
               }else{
                   _menu.className = "focused";
               }
           }
       }
   }

}