这是一个方法:<input type=button onclick="document.all.layer57.innerHTML+='<br>'" value="增加内容">
<br>
<div id="layer57" style="position:absolute; width:50%; height:50%; z-index:1; overflow: auto; visibility: visible;">
<br><br><br><br><br><br><br><br><br><br><br><br><br>
</div>
<script language="JavaScript">
var apear=false;
function checkscroll(){
var cH=document.all.layer57.clientHeight;
var sH=document.all.layer57.scrollHeight;
if(cH<sH&&apear==false){apear=true;alert("出现了");}
if(cH>=sH&&apear==true){apear=false;alert("消失了");}
var aa=setTimeout("checkscroll()",250);
}
checkscroll();
</script>笨方法
<br>
<div id="layer57" style="position:absolute; width:50%; height:50%; z-index:1; overflow: auto; visibility: visible;">
<br><br><br><br><br><br><br><br><br><br><br><br><br>
</div>
<script language="JavaScript">
var apear=false;
function checkscroll(){
var cH=document.all.layer57.clientHeight;
var sH=document.all.layer57.scrollHeight;
if(cH<sH&&apear==false){apear=true;alert("出现了");}
if(cH>=sH&&apear==true){apear=false;alert("消失了");}
var aa=setTimeout("checkscroll()",250);
}
checkscroll();
</script>笨方法
解决方案 »
免费领取超大流量手机卡,每月29元包185G流量+100分钟通话, 中国电信官方发货