.html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>
<head>
<meta http-equiv="content-type" content="text/html;charset=gbk"/>
<title>RegExp用法</title>
<script type="text/javascript">
function chkEmail(){
var email = document.getElementById('email').value;
var obj = document.getElementById('showMess');
//www@163.com
var pattern = /^[a-zA-Z]\w+[@]\w+[.][\w.]+$/;//<pre name="code" class="html">^[a-zA-Z]<span style="font-family: Arial, Helvetica, sans-serif;">表示以字母开头</span>
if(pattern.test(email)){obj.innerText = "正确";obj.style.color = 'green';}else{obj.innerText = "错误";obj.style.color = 'red';}}</script></head><body><label>电子邮件:</label><input type="text" id="email" οnblur="chkEmail()"/><span id="showMess"></span></body></html>
结果如下：
