为啥我写的没办法验证
<!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>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style type="text/css">
body, form, input{margin:0;padding:0;font-size:12px}
body{ margin-left:50px}
form{ height:30px; line-height:30px}
.text{height:20px; vertical-align:middle}
.btn{ height:24px;width:50px;vertical-align:middle; border:1px solid #333; background:#ccc;}
</style>
</head>
<script type="text/javascript">
window.onload=function(){
var oBtn=document.getElementById('submitBtn');
var oInput=document.getElementById('name');
oBtn.olnput=function(){
var re =/^[a-zA-Z]{1}[\w\_\.]{4,19}$/g;
if(re.test(oInput.value)==false){
alert("× 格式错误！")
}
else{
alert("√ 格式正确！")
}
}
}
</script>
<body>
<h3>要求：</h3>
<p>1. 只能输入5-20个字符，必须以“字母”开头</p>
<p>2. 可以带“数字" “_” “.”的字串</p>
<br />
<form>
<label>用户名：<input id="name" class="text" type="text" /></label> <input id="submitBtn" class="btn" type="button" value="验证" />
</form>
</body>
</html>
