<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title></title>
<style>
#div1 {
height: 200px;
background-color: #bbbbbb;
font-size: 100px;
}
</style>
</head>
<body style="height:3500px">
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<div id="div1">
我是div1
</div>
<script type="text/javascript">
var ele = document.getElementById(‘div1‘);
//ele.offsetTop;
//ele.offsetLeft;
//ele.offsetHeight;
//ele.offsetParent;
function offset(ele) {
var t = ele.offsetTop;
var l = ele.offsetLeft;
var p = ele.offsetParent;
while (p) {
if (window.navigator.userAgent.indexOf(‘MSIE 8‘) > -1) {
l += p.offsetLeft;
t += p.offsetTop;
} else {
l += p.offsetLeft + p.clientLeft;
t += p.offsetTop + p.clientTop;;
}
p = p.offsetParent;
}
return { left: l, top: t };
}
var h = offset(ele).top + ele.offsetHeight;//这是这个元素底边距文档顶部的绝对偏移量
window.onscroll = function () {
var winBottom = (document.documentElement.scrollTop || document.body.scrollTop) + (document.documentElement.clientHeight || document.body.clientHeight);
if (h<winBottom) {
ele.innerHTML = "哈哈，我来也";
}
}
//var h = ht(ele).top + ele.offsetHeight;
//window.onscroll = function () {
//}
</script>
</body>>
</html>
原文：http://www.cnblogs.com/alphafly/p/4688408.html