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++)
{
document.write("document.all["+i+"]="+document.all[i].tagName+"<br />");
}//--></script></body></html>输出结果： Example Heading--------------------------------------------------------------------------------This is a paragraph. It is only a paragraph.Yet another paragraph.This final paragraph has special emphasis.--------------------------------------------------------------------------------document.all.length=18document.all[0]=!document.all[1]=HTMLdocument.all[2]=HEADdocument.all[3]=TITLEdocument.all[4]=METAdocument.all[5]=BODYdocument.all[6]=H1document.all[7]=HRdocument.all[8]=Pdocument.all[9]=EMdocument.all[10]=EMdocument.all[11]=Pdocument.all[12]=EMdocument.all[13]=Pdocument.all[14]=EMdocument.all[15]=EMdocument.all[16]=HRdocument.all[17]=SCRIPT 例2（访问一个特定元素）<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=gb2312"><title>单击DIV变色</title><style type="text/css"><!--#docid{height:400px;width:400px;background-color:#999;}--></style></head><body><div id="docid" name="docname" onClick="bgcolor()"></div></body></html><script language="javascript" type="text/javascript"><!--function bgcolor(){document.all[7].style.backgroundColor="#000"}--></script> 上面的这个例子让你了解怎么访问文档中的一个特定元素，比如文档中有一个DIV<div id="docid" name="docname"></div>，你可以通过这个DIV的ID，NAME或INDEX属性访问这个DIV：document.all["docid"]document.all["docname"]document.all.item("docid")document.all.item("docname")document.all[7]document.all.tags("div")则返回文档中所有DIV数组，本例中只有一个DIV，所以用document.all.tags("div")[0]就可以访问了。 2、使用document.all[]例3<!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 #2</title><meta http-equiv="content-type" content="text/html; charset=ISO-8859-1" /></head><body><!-- Works in Internet Explorer and compatible --><h1 id="heading1" align="center" style="font-size: larger;">DHTML Fun!!!</h1><form name="testform" id="testform" action="#" method="get"><br /><br /><input type="button" value="Align Left" onclick="document.all['heading1'].align='left';" /><input type="button" value="Align Center"onclick="document.all['heading1'].align='center';" /><input type="button" value="Align Right"onclick="document.all['heading1'].align='right';" /><br /><br /><input type="button" value="Bigger"onclick="document.all['heading1'].style.fontSize='xx-large';" /><input type="button" value="Smaller"onclick="document.all['heading1'].style.fontSize='xx-small';" /><br /><br /><input type="button" value="Red"onclick="document.all['heading1'].style.color='red';" /><input type="button" value="Blue"onclick="document.all['heading1'].style.color='blue';" /><input type="button" value="Black"onclick="document.all['heading1'].style.color='black';" /><br /><br /><input type="text" name="userText" id="userText" size="30" /><input type="button" value="Change Text"onclick="document.all['heading1'].innerText=document.testform.userText.value;" /></form></body></html>