1、理解document.all[] 从IE4开始IE的object model才增加了document.all[],来看看document.all[]的Description: Array of all HTML tags in the document.Collection of all elements contained by the object. 也就是说document.all[]是文档中所有标签组成的一个数组变量，包括了文档对象中所有元素（见例1）。 IE’s document.all collection exposes all document elements.This array provides access to every element in the document. document.all[]这个数组可以访问文档中所有元素。 例1（这个可以让你理解文档中哪些是对象） <!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> <title>Document.All Example</title> <meta http-equiv="content-type" content="text/html; charset=ISO-8859-1"/> </head> <body> <h1>Example Heading</h1> <hr /> <p>This is a <em>paragraph</em>. It is only a <em>paragraph.</em></p> <p>Yet another <em>paragraph.</em></p> <p>This final <em>paragraph</em> has <em id="special">special emphasis.</em></p> <hr /> <script type="text/javascript"> <!-- var i,origLength; origLength = document.all.length; document.write('document.all.length='+origLength+"<br />"); for (i =0; i < origLength; i++)