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老师批语：
1.问答: Ajax的工作原理分析(用自己语言组织):
Ajax:异步处理JavaScript数据和XML结构数据,kehu端和服务器可以同时处理"不同的请求",然后通过事件监听事件来判断数据是否返回.
2.编程: Ajax用户登录验证:
(前端):
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Ajax实战</title>
</head>
<body>
<h3>用户登陆</h3>
<form method="post">
<p><input type="text" name="email" placeholder="邮箱地址"></p>
<p><input type="password" name="password" placeholder="密码"></p>
<p><button type="button">登录</button></p>
</form>
<script>
let btn = document.getElementsByTagName('button')[0];
btn.onclick = function () {
//1.创建xrh监听事件
let xhr = new XMLHttpRequest();
//2.监听响应状态
xhr.onreadystatechange = function () {
if (xhr.readyState === 4) {
//判断是否获取到了响应的数据
if (xhr.status === 200) {
let p = document.createElement('p');
p.style.color = 'red';
//从服务器取回数据
let json = JSON.parse(xhr.responseText);
if (json.status === 1) {
p.innerHTML = json.msg;
} else if (json.status == 0) {
p.innerHTML = json.msg;
}
//将新元素,获取到的内容插入到当前页面中
document.forms[0].appendChild(p);
btn.disabled = true;//
setTimeout(function () {
},2000)
}
else {
alert('响应失败:'+xhr.status);
}
} else {
}
};
//3.设置请求参数
xhr.open('post', 'inc/check.php', true);
//4.设置头信息,将内容类型设置为表单提交方式
xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
let data = {
email: document.getElementsByName('email')[0].value,
password: document.getElementsByName('password')[0].value
};
//将内容转换成json字符串类型
let data_Json = JSON.stringify(data);
//5.发送请求
xhr.send('data=' + data_Json);
btn.setAttribute('disable', true);
}
</script>
</body>
</html>点击 "运行实例" 按钮查看在线实例
(后端):
<?php
//登录验证
//print_r($_POST['data']);
$user = json_decode($_POST['data']);//将json字符串转换成php对象
$email = $user->email;
$password = sha1($user->password);
echo $user->email;
echo $user->password;
$pdo = new PDO("mysql:host=127.0.0.1;daname=php",'root','root');
$sql = "SELECT COUNT(*) FROM `user` WHERE `email`={$email} AND `password`={$password}";
$stmt = $pdo->prepare($sql);
$stmt->execute();
//判断邮箱和密码是否正确
if ($stmt->fetchColumn(0)==1) {
echo json_encode(['status'=>1,'msg'=>'登录成功,正在跳转']);
exit;
} else {
echo json_encode(['status'=>0,'msg'=>'登录失败,正在跳转']);
exit;
}点击 "运行实例" 按钮查看在线实例
3.手写: Ajax的完整运行流程(以get为例)，共四步。
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