a.html
<!DOCTYPE html>
<html>
<head>
<title></title>
</head>
<body>
<div id="a">hello world!!!</div>
<div id="b">
<iframe id="frm" name="frm" src="b.html"></iframe>
</div>
</body>
</html>
b.html
<!DOCTYPE html>
<html>
<head>
<title></title>
<script type="text/javascript" src="jquery.js" ></script>
<script type="text/javascript">
function aa(){
//获取本页面的元素
//var a = document.getElementById("a12").innerHTML;
//获取父页面的元素
//方法一
//var a = $(window.parent.document).find("#a").text();
//方法二
var a = $("#a",window.parent.document).text();
alert(a);
}
</script>
</head>
<body>
<div id="a12">哈哈</div>
<div>
<div id="btn" onclick="aa()">点击</div>
</div>
</body>
</html>