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老师批语：程序最终是要给人用的, 一定要站在用户的角度看问题, 尽可能的将可能的意外考虑进去, 永远不要相信用户的输入, 这是一个基本原则和开发前掉
一.Ajax-GET
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<label for="username">username</label>
<input type="text" id="username" class="username" autofocus>
<p id="contains"></p>
<script>
//获取输入框
var input=document.getElementById("username");
//获取p标签
var contains=document.getElementById("contains")
//1.创建请求对象
var request=new XMLHttpRequest();
input.addEventListener('keypress',getcontains,false);
function getcontains(event) {
if(event.key==="Enter"){
switch (true) {
//判断是否为空
case input.value.length === 0:
contains.innerHTML = '<span style="color:red">ID为空!</span>';
return false;
// 判断是否为整数
case isNaN(input.value):
contains.innerHTML = '<span style="color:red">ID不是整数！</span>';
return false;
default:
//2.监听:成功回调
request.addEventListener('readystatechange',successCallback,false);
//3.设置:请求参数 对数据进行编码处理
var data=encodeURIComponent(input.value);
request.open('GET','1.php?user_id='+data,true);
//4.发送:异步请求;
request.send(null);
}
}
}
//成功的回调函数
function successCallback(event){
if(request.readyState===4){
contains.innerHTML=request.responseText;
}
}
//为input添加事件每次重新输入input内容,清空contains内的提示或信息
input.addEventListener('input',clr,false);
function clr(event){
contains.innerHTML=null;
}
</script>
</body>
</html>点击 "运行实例" 按钮查看在线实例
<?php
$userId = isset($_GET['user_id']) ? $_GET['user_id'] : null;
$userInfo = [
['user_id' => 1, 'username' => '苍老师', 'gender' => '女', 'age' => 26],
['user_id' => 2, 'username' => '波老师', 'gender' => '女', 'age' => 23],
['user_id' => 3, 'username' => '黑老师', 'gender' => '男', 'age' => 33],
];
$res = '';
foreach ($userInfo as $user) {
if ($user['user_id'] === intval($userId)) {
$res .= $user['user_id'] . '---' . $user['username'] . '---' . $user['gender'] . '---' . $user['age'];
}
}
echo empty($res) ? '<span style="color: red;">没有找到该用户名</span>' : $res;
exit;
?>点击 "运行实例" 按钮查看在线实例
二.一.Ajax-GET
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style type="text/css">
</style>
</head>
<body>
<h2>login</h2>
<form action="" name="login">
<p>
<label for="username">username:</label><br>
<input type="text" name="username" id="username" placeholder="input username">
</p>
<p>
<label for="email">email:</label><br>
<input type="text" name="email" id="email" placeholder="example@email.com">
</p>
<p>
<label for="password">password:</label><br>
<input type="password" name="password" id="password">
</p>
<p>
<label for="remember">记住我:</label>
<select name="remember" id="remember">
<option value="1" selected>1</option>
<option value="7">7</option>
<option value="30">30</option>
</select>
</p>
<p>
<button type="button" name="submit">提交</button>
</p>
</form>
<script>
var login=document.forms.namedItem("login");
var btn=login.submit;
var request=new XMLHttpRequest();
login.username.addEventListener('blur',cck,false);
login.email.addEventListener('blur',cck,false);
login.password.addEventListener('blur',cck,false);
function cck(event){
if(event.target.value.length===0){
if(event.target.nextElementSibling===null){
var contains=document.createElement("span");
contains.style.color="red";
switch(event.target.name){
case 'username':
contains.innerText="username not allow empty";
break;
case 'email':
contains.innerText="email not allow empty";
break;
case 'password':
contains.innerText="password not allow empty";
break;
default:
contains.innerText="unknown error";
}
event.target.parentNode.appendChild(contains);
}
//焦点聚集于错误输入框上
event.target.focus();
}
}
login.username.addEventListener('input',clr,false);
login.email.addEventListener('input',clr,false);
login.password.addEventListener('input',clr,false);
function clr(event){
var contains=event.target.nextElementSibling;
if(contains!==null){
contains.parentNode.removeChild(contains);
}
}
btn.addEventListener('click',check,false);
function check(event) {
var username=login.username.value;
var email=login.email.value;
var password=login.password.value;
var remember=login.remember.value;
if (username.length === 0 || email.length === 0 || password.length === 0) {
btn.removeEventListener('click',check,false);
var blurEvent=new Event('blur');
login.username.dispatchEvent(blurEvent);
return false;
}
// 2.监听:成功回调
request.addEventListener('readystatechange', successCallback, false);
// 3.设置:请求参数
request.open('POST', 'php/check.php', true);
//设置请求头部
request.setRequestHeader('content-type','application/x-www-form-urlencoded;charset=utf-8');
//4.发送:异步请求
var data = 'username='+username+'&email='+email+'&password='+password+'&remember='+remember;
request.send(data);
}
function successCallback(event){
if(request.readyState===4){
console.log(request.responseText);
}
}
</script>
</body>
</html>点击 "运行实例" 按钮查看在线实例
<?php
session_start();
// 获取表单提交的数据
$username = $_POST['username'];
$email = $_POST['email'];
$password = sha1($_POST['password']);
$remember = $_POST['remember'];
// 为简化代码,不用数据表验证,使用硬编码,只验证邮箱与密码
if ($email === 'admin@php.cn' && $password === sha1('123456')) {
$_SESSION['username'] = $username;
$_SESSION['email'] = $email;
echo json_encode(['status'=>1, 'message'=>'验证成功']);
} else {
echo json_encode(['status'=>0, 'message'=>'验证失败']);
}
exit;点击 "运行实例" 按钮查看在线实例
总结:
1.Ajax-Get/Post请求基本步骤
（1）创建: 请求对象 var request = new XMLHttpRequest();
（2）监听: 成功回调
request.addEventListener('readstatechange', successCallback, false);
function successCallback(ev) {
if (request.readyState === 4) {
console.log(request.responseText);
}
}（3）设置: 请求参数
open(method,url,bool) method:请求类型 url:文件位置 bool：true异步/false同步
（4）发送: 请求
request.send();
其实GET与Post请求写法上并没有太大差距
POST与GET相比需要设置请求头以及发送请求时携带参数的写法稍微有点区别
2.当使用POST方法时候需要设置请求头部
setRequestHeader(header,value) header:头名称 value:规定头的值
request.setRequestHeader('content-type', 'application/x-www-form-urlencoded;charset=utf-8');
3.Ajax的onreadystatechange事件
每当 readyState 改变时，就会触发 onreadystatechange 事件。
readyState 0: 请求未初始化 1: 服务器连接已建立 2: 请求已接收 3: 请求处理中 *4: 请求已完成，且响应已就绪
status 200: "OK" 404: 未找到页面
4.Ajax的服务端响应
如果需要获得来自服务器的响应，需要使用 XMLHttpRequest 对象的 responseText 或 responseXML 属性。
responseText 获得字符串形式的响应数据
responseXML 获得XML形式的响应数据
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