JS 版
<!DOCTYPE html>
<html>
<head>
<style type="text/css">
#showIt {
width: 200px;
height: 200px;
background-color: red;
position: absolute;
top: 1500px;
}
</style>
</head>
<body style="height:2000px;">
<div id="showIt"></div>
</body>
<script type="text/javascript">
document.onscroll = function() {
var scrollTop = document.documentElement.scrollTop || document.body.scrollTop;
var cHeight = window.innerHeight || document.documentElement.clientHeight || document.body.clientHeight;
var oDiv = document.getElementById('showIt');
if (scrollTop > (oDiv.offsetTop - cHeight))
alert('触发了')
}
</script>
</html>
JQ版
$(document).scroll(function() { sTop = $(this).scrollTop(); //获取滚动条的位置 var sh = $(window).height();//视口高度 var ft = $("footer").offset().top//指定元素距离文档顶部高度 // 滚动条位置 大于 指定元素减去 视口高度时 if (sTop > (ft - sh)) { //当底部出现在视口时 触发 //dododo } }