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老师批语：对于Ajax,重点掌握它的步骤, 还是常用的几个属性和方法, 必须背下来
动态获取用户信息：
基本步骤：1.创建: 请求对象 2.监听: 成功回调 3.设置: 请求参数 4.发送: 异步请求
innerHTML支持HTML标签 isNaN判断是否为数值 readystatechange successCallback 成功回调
encodeURIComponent():对值中的非法字符进行编码,如空格等,解码:decodeURIComponent()
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Ajax-GET</title>
</head>
<body>
<label for="user_id">用户ID：</label>
<input type="text" id="user_id" name="user_id" autofocus>
<p id="tips"></p>
<script>
var input = document.getElementById("user_id");
var tips = document.getElementById('tips');
// 1. 创建: 请求对象
var request = new XMLHttpRequest();
input.addEventListener('keyPress',getUserInfo,false);
function getUserInfo(ev) {
if (ev.key === 'Enter'){
switch (true) {
case input.value.length === 0:
tips.innerHTML ='<span style="color: red">ID不能为空</span>';
return false;
case isNaN(input.value):
tips.innerHTML = "<span style='color: red'>ID必须为整数</span>"
return false;
default:
request.addEventListener('readystatechange',successCallback,false);
var data = encodeURIComponent(input.value);
request.open('GET','php/user_info.php?user_id='+data,true);
request.send(null);
}
}
}
function successCallback() {
if (request.readyState === 4){
tips.innerHTML = request.responseText;
}
}
input.addEventListener('input',function () {
tips.innerHTML = null;
},false);
</script>
</body>
</html>点击 "运行实例" 按钮查看在线实例
2.post方式表单验证：
基本步骤：1.创建: 请求对象 2.监听: 成功回调 3.设置: 请求参数 4.发送: 异步请求 5.设置请求头类型
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>post</title>
</head>
<body>
<h2>用户登录</h2>
<form action="" name="login">
<p>
<label for="username">用户:</label>
<input type="text" name="username" id="username" placeholder="UserName">
</p>
<p>
<label for="email">邮箱:</label>
<input type="text" name="email" id="email" placeholder="example@email.com">
</p>
<p>
<label for="password">密码:</label>
<input type="password" name="password" id="password" placeholder="******" >
</p>
<p>
<label for="remember">记住我:</label>
<select name="remember" id="remember">
<option value="1" selected>一天</option>
<option value="7">一星期</option>
<option value="30">一个月</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', isEmpty, false);
login.email.addEventListener('blur', isEmpty, false);
login.password.addEventListener('blur', isEmpty, false);
function isEmpty(ev) {
if (ev.target.value.length === 0) {
if (ev.target.nextElementSibling === null) {
var tips = document.createElement('span');
tips.style.color = 'red';
switch (ev.target.name) {
case 'username':
tips.innerText = '用户名不能为空';
break;
case 'email':
tips.innerText = '邮箱不能为空';
break;
case 'password':
tips.innerText = '密码不能为空';
break;
default:
tips.innerText = '未定义错误';
}
ev.target.parentNode.appendChild(tips);
}
ev.target.focus();
}
}
login.username.addEventListener('input', clearTips, false);
login.email.addEventListener('input', clearTips, false);
login.password.addEventListener('input', clearTips, false);
function clearTips(ev) {
var tips = ev.target.nextElementSibling;
if (tips !==null){
tips.parentNode.removeChild(tips);
}
}
btn.addEventListener('click',check,false);
function check(ev) {
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){
ev.target.removeEventListener('click',check,false);
var blurEvent = new Event('BLUR');
login.username.dispatchEvent(blurEvent);
return false;
}
var data = 'username='+username+'&email='+email+'&password='+password+'&remember='+remember;
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) {
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
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