IE 事件兩次響應

var throldHold = 20; //兩次scroll事件觸發之間最小的事件間隔window.onscroll = function(){    if(arguments.callee.timer) clearTimeout(arguments.callee.timer);    arguments.callee.timer = setTimeout(function(){        var tops =0;        if(document.body.scrollTop){            tops = document.body.scrollTop;        }        else{            tops = document.documentElement.scrollTop;        }                if(tops >= document.documentElement.scrollHeight - document.documentElement.clientHeight){            var ss="1";            document.title +=ss;        }    },throldHold);}