<!DOCTYPE HTML>
<html lang="en-US">
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<script type="text/javascript">
/*
alert( 1988 == "1988");//没有比较类型所以返回true
alert( 1988 === "1988");//类型比较返回false
*/
/*
var o = new Object;
o.name = "David";
alert(o.name); //输出 "David"
delete o.name;
alert(o.name); //输出 "undefined"
*/
/*
//与
document.write( 10 > 1 && 10 > 2);
document.write("<br/>");
//或
document.write( 10 < 1 || 10 < 2);
document.write("<br/>");
//非（取反）
document.write( 10 != 100);
document.write("<br/>");
*/
//验证表单
function checkChange(){
var username = document.getElementById("username");
if(username.value == "admin" || username.value == "xiaozhanga4"){
alert("恭喜你," + username.value );
}else{
alert("用户名不能为空");
}
}
</script>
<form action="" method="post">
<input type="text" id="username" name="username"/>
<input type="submit" value="submit" onclick="checkChange();"/>
</form>
</body>
</html>