這樣我就不理解這個代碼為啥能停止了
window.onscroll = function(){
var scrDis = document.documentElement.scrollTop || document.body.scrollTop;
if(scrDis>=clientHeight){
btn.style.display = 'block';
}else{
btn.style.display = 'none';
}
if(!noStop){
clearInterval(timer);
}
noStop = false;
};