Question

javascript 中js调试

var lastScrollYser = 0;
function heartBeatser()
{
diffY = document.body.scrollTop+document.documentElement.scrollTop;
var obj = document.getElementById("mqq");

var percent =1*(diffY-lastScrollYser);
if(percent>0)
{ percent = Math.ceil(percent); }
else
{ percent = Math.floor(percent);}
obj.style.top = (parseInt(obj.style.top,10)+percent)+"px";
lastScrollYser = lastScrollYser+percent;
}
obj.style.top = (parseInt(obj.style.top,10)+percent)+"px";这一行缺少对象？

Answer 1

var lastScrollYser = 0;
var percent = 0;
var obj = document.getElementById("mqq");

function heartBeatser()
{
diffY = document.body.scrollTop+document.documentElement.scrollTop;
percent =1*(diffY-lastScrollYser);
if(percent>0)
{ percent = Math.ceil(percent); }
else
{ percent = Math.floor(percent);}
obj.style.top = (parseInt(obj.style.top,10)+percent)+"px";
lastScrollYser = lastScrollYser+percent;
}
obj.style.top = (parseInt(obj.style.top,10)+percent)+"px";

Answer 2

加个if(obj),试下。
if(obj)
{
obj.style.top = (parseInt(obj.style.top,10)+percent)+"px";
}

Answer 3

var obj = document.getElementById("mqq");
放到函数外面来
即：
var obj = document.getElementById("mqq");

function heartBeatser()
{

追问

不行

追答

var percent =1*(diffY-lastScrollYser);
也要放到外面来