```html
<!DOCTYPE html>
<html lang="cn">
<head>
<meta charset="UTF-8">
<title>馨云教务管理系统</title>
<link rel="stylesheet" href="./style.css">
<script src="script.js" type="text/javascript"></script>
<script src='https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.0/jquery.min.js'></script>
</head>
<body>
<div class="container">
<div class="welcome">
<div class="pinkbox">
<!-- 注册 -->
<div class="signup nodisplay">
<h1>注 册</h1>
<form autocomplete="off">
<input type="text" placeholder="用户名">
<input type="email" placeholder="邮 箱">
<input type="password" placeholder="密 码">
<input type="password" placeholder="确认密码">
<button class="button submit">创建用户</button>
</form>
</div>
<!-- 登录 -->
<div class="signin">
<h1>登 录</h1>
<form class="more-padding" >
<input type="text" id="login_username" placeholder="用户名">
<input type="password" id="login_password" placeholder="密 码">
<div class="checkbox">
<input type="checkbox" id="remember" /><label for="remember">记住登录状态</label>
</div>
<button class="buttom sumbit" id="login">登 录</button>
</form>
</div>
</div>
<div class="leftbox">
<h2 class="title"><span>馨 云</span><br>教务管理系统</h2>
<p class="desc">欢迎来到 <span>馨云</span></p>
<img class="flower smaller" src="./webp.webp" />
<p class="account">已有账户</p>
<button class="button" id="signin">登 录</button>
</div>
<div class="rightbox">
<h2 class="title"><span>馨 云</span><br>教务管理系统</h2>
<p class="desc">欢迎来到<span>馨云</span></p>
<img class="flower" src="./webp (1).webp" />
<p class="account">没有账户?</p>
<button class="button" id="signup">注 册</button>
</div>
</div>
</div>
<!-- partial -->
<script src='https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.0/jquery.min.js'></script><script src="./script.js"></script>
</body>
</html>
```javascript
$('#login').click(function (){
var user = $('#login_username').value
var pass = $('#login_password').text
alert($('#login_username').value)
// if (user === null || user === undefined || user === "" ) {
// alert("用户名不能为空")
// } else if (pass === null || pass === undefined || user === "") {
// alert("密码不能为空")
// }
});
直接alert(user)
alert($('#login_username').value)
尚未赋值 所以默认值是underfined
var pass = $('#login_password').text
末尾是不是可以更改为. value
你这jquery选择的id也不对呀，如果你打印表单，就把id=“login”写上，然后打印的时候直接打印变量user即可