用户名判断（练习）
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<input type="text" id="username"><span id="show"></span>
<script>
function $(id){
return document.getElementById(id);
}
var username=$("username");
var show=$("show");
var http=new XMLHttpRequest;
username.onblur=function(){
http.open("GET","a.php?username="+this.value,true);
http.send();
}
http.onreadystatechange=function(){
if(this.readyState==4 && this.status==200){
if(this.responseText=="0"){
show.innerHTML="ok";
}
else{
show.innerHTML="error";
}
}
}
</script>
</body>
</html>
php:
<?php
if($_GET["username"]){//定义用户名
$a=$_GET["username"];//用户名赋给$a
if($a=="admin"){//判断接受的用户名是否是admin
echo "0"; //正确返回1
}
else{
echo "1";//不是返回0
}
}
?>
