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<!DOCTYPE html>
<html lang="en">
<head>
<title>Document</title>
</head>
<script src="./1.js"></script>
<body>
<strong>用户名：</strong> <input type="text" id="username" onblur="USN()"> <span id="a"></span><br>
<strong>密码： </strong> <input type="password" id="pwd" onblur="PWD()"><span id="b"></span><br>
<strong>确认密码：</strong> <input type="password" id="confirmpwd"><span id="c"></span><br>
<strong>邮件地址：</strong> <input type="text" id="email" onblur="EMAIL()"><span id="d"></span>
</body>
</html>JavaScript
function USN()
{
var x = document.getElementById("username").value;
var reg=/^[a-zA-Z]\S+/;
if(!reg.test(x))
document.getElementById("a").innerHTML="用户名只能以字母开头";
else if(x.length < 6 || x.length > 20)
document.getElementById("a").innerHTML="用户名长度大于6小于20";
else
document.getElementById("a").innerHTML="";
}
function PWD()
{
var x = document.getElementById("pwd").value;
var y = document.getElementById("username").value;
if(x == y)
document.getElementById("b").innerHTML="密码不能和用户名相同";
else if(x.length < 6 || x.length > 20)
document.getElementById("b").innerHTML="密码长度大于6小于20";
else
document.getElementById("b").innerHTML="";
}
function EMAIL()
{
var x = document.getElementById("email").value;
var reg = /^\w{1,15}(?:@(?!-))(?:(?:[a-z0-9-]*)(?:[a-z0-9](?!-))(?:\.(?!-)))+[a-z]{2,4}$/;
if(!reg.test(x))
document.getElementById("d").innerHTML="请输入正确的电子邮箱";
else
document.getElementById("d").innerHTML="";
}