用document.documentElement取代document.body的原因分析

IE6在页面内容超出窗口大小时将宽度属性scrollWidth、clientWidth、offsetWidth都解释为内容实际宽度。
上次的测试说明了document.body属性并不会给我们返回预期的结果,比如我们用document.body.clientHeight原本想取得“页面可见区域高度”,可实际上返回的是“页面实际内容高度”。
那我们怎么办呢?难道加上了文档DTD类型之后就再也不能取到“可见区域高度”和“内容实际宽度”等等属性了吗?

复制代码 代码如下:


<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>documentElement</title>
<style type="text/css">
body{margin:0;padding:0;font:12px/150% arial;}
</style>
<script type="text/javascript">
function a() {
var scrollTop;
var scrollLeft;
if (typeof window.pageYOffset != 'undefined') {
scrollTop = window.pageYOffset;
scrollLeft = window.pageXOffset;
}
else if (typeof document.compatMode != 'undefined' && document.compatMode != 'BackCompat') {
scrollTop = document.documentElement.scrollTop;
scrollLeft = document.documentElement.scrollLeft;
}
else if (typeof document.body != 'undefined') {
scrollTop = document.body.scrollTop;
scrollLeft = document.body.scrollLeft;
}
var scrollHeight = document.documentElement.scrollHeight;
var scrollWidth = document.documentElement.scrollWidth;
var clientWidth = document.documentElement.clientWidth;
var clientHeight = document.documentElement.clientHeight;
var offsetWidth = document.documentElement.offsetWidth;
var offsetHeight = document.documentElement.offsetHeight;
var screenTop = window.screenTop;
var screenBottom = window.screenBottom;
var screenLeft = window.screenLeft;
var sheight = window.screen.height;
var swidth = window.screen.width;
var availHeight = window.screen.availHeight;
var availWidth = window.screen.availWidth;
document.getElementById('scrollTop').value = scrollTop;
document.getElementById('scrollLeft').value = scrollLeft;
document.getElementById('scrollHeight').value = scrollHeight;
document.getElementById('scrollWidth').value = scrollWidth;
document.getElementById('clientWidth').value = clientWidth;
document.getElementById('clientHeight').value = clientHeight;
document.getElementById('offsetWidth').value = offsetWidth;
document.getElementById('offsetHeight').value = offsetHeight;
document.getElementById('screenTop').value = screenTop;
document.getElementById('screenBottom').value = screenBottom;
document.getElementById('screenLeft').value = screenLeft;
document.getElementById('sheight').value = sheight;
document.getElementById('swidth').value = swidth;
document.getElementById('availHeight').value = availHeight;
document.getElementById('availWidth').value = availWidth;
}
</script>
</head>
<body>
<div>
<center>
<table cellspacing="0" cellpadding="0">
<tr>
<td>scrollTop(滚动条卷过的高):</td>
<td> </td>
<td><input type="text" /></td>
</tr>
<tr>
<td>scrollLeft(滚动条卷过的宽):</td>
<td> </td>
<td><input type="text" /></td>
</tr>
<tr>
<td>scrollHeight(内容实际高度):</td>
<td> </td>
<td><input type="text" /></td>
</tr>
<tr>
<td>scrollWidth(内容实际宽度):</td>
<td> </td>
<td><input type="text" /></td>
</tr>
<tr>
<td>clientWidth(可见区域宽):</td>
<td> </td>
<td><input type="text" /></td>
</tr>
<tr>
<td>clientHeight(可见区域高):</td>
<td> </td>
<td><input type="text" /></td>
</tr>
<tr>
<td>offsetWidth(加滚动条宽?):</td>
<td> </td>
<td><input type="text" /></td>
</tr>
<tr>
<td>offsetHeight(加滚动条高?):</td>
<td> </td>
<td><input type="text" /></td>
</tr>
<tr>
<td>screenTop:</td>
<td> </td>
<td><input type="text" /></td>
</tr>
<tr>
<td>screenBottom:</td>
<td> </td>
<td><input type="text" /></td>
</tr>
<tr>
<td>screenLeft:</td>
<td> </td>
<td><input type="text" /></td>
</tr>
<tr>
<td>sheight(分辨率高):</td>
<td> </td>
<td><input type="text" /></td>
</tr>
<tr>
<td>swidth(分分辨率宽):</td>
<td> </td>
<td><input type="text" /></td>
</tr>
<tr>
<td>availHeight:</td>
<td> </td>
<td><input type="text" /></td>
</tr>
<tr>
<td>availWidth:</td>
<td> </td>
<td><input type="text" /></td>
</tr>
</table>
<a href="javascript:a()">内容高度是400PX,点击查看所有属性值</a>
</center>
</div>
</body>
</html>


其实,我们可以用document.documentElement代替document.body来获取我们想要的结果 将代码中的document.body替换为document.documentElement,再来看看各浏览器下的实际结果:
ii测试结果表明,IE系列浏览器对document.documentElement属性的解释是正确的,其它标准浏览器将offsetHeight解释成 了scrollHeight。火狐和netscape更是把这两个属性调换了过来。不过总的来说各属性都可以有个相应的解释,不会像 document.body一样只有可怜的两种解释。

终于可以放心地使用JS方法获取各种页面高宽属性了吧^_^!

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