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老师批语：Ajax的本质是异步, 但异步执行的不一定都是Ajax, Ajax只是实现异步编程的一种手段罢了
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>ajax验证</title>
</head>
<body>
<h1>用户注册</h1>
<form action="" name="register">
<p>
<label for="username">用户名：</label>
<input type="text" name="username" id="username">
</p>
<p>
<label for="password">密码:</label>
<input type="password" name="password" id="password">
</p>
<button type="button" name="submit">注册</button>
</form>
<script>
var register=document.forms.namedItem('register');
var input =document.getElementById('username');
var password =document.getElementById('password');
var btn = login.submit;
var request= new XMLHttpRequest();
input.addEventListener('focus', function (ev) {
ev.target.style.backgroundColor = 'lightgreen';
}, false);
input.addEventListener('blur', function (ev) {
return ev.target.value.length === 0 ? alert('不能为空') : false;
}, false);
password.addEventListener('focus',function(ev){ ev.target.style.backgroundColor = 'lightgreen';
}, false);
password.addEventListener('blur', function (ev) {
return ev.target.value.length === 0 ? alert('不能为空') : false;
}, false);
request.addEventListener('readstatechange', successCallback, false);
function successCallback(ev) {
if (request.readyState === 4) {
console.log(request.responseText);
}
}
btn.addEventListener('click', check, false);
function check(ev) {
var username = login.username.value;
var password = login.password.value;
if (username.length === 0 || password.length === 0) {
ev.target.removeEventListener('click', check, false);
var blurEvent = new Event('blur');
login.username.dispatchEvent(blurEvent);
return false;
}
var data = 'username='+username+'&password='+password+';
request.addEventListener('readystatechange', successCallback, false);
request.open('POST', 'php/check.php', true);
request.setRequestHeader('content-type', 'application/x-www-form-urlencoded;charset=utf-8');
request.send(data);
}
function successCallback(ev) {
// console.log(ev.target);
if (request.readyState === 4) {
var obj = JSON.parse(request.responseText);
var tips = document.createElement('span');
var url = '';
switch (obj.status) {
case 1:
tips.style.color = 'green';
tips.innerText = obj.message+',正在跳转...';
url = 'php/admin.php';
break;
case 0:
tips.style.color = 'red';
tips.innerText = obj.message;
url = 'demo1.html'; // 也可以重新加载本页面
break;
default:
console.log('未知错误');
break;
}
btn.parentNode.appendChild(tips);
setTimeout(function () {
location.href = url;
}, 3000);
}
}
</script>
</body>
</html>点击 "运行实例" 按钮查看在线实例
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