为什么我的JS代码不起作用,哭了,大佬们看一下

<head>
<meta charset="UTF-8">
<title>js</title>
<script type="text/javascript">
   function checkUser(){
       var username= document.getElementById("username").value;      
       var password=document.getElementById("password").value;
       alert(username+"=="+password);
   }
</script>
</head>
<body>
<form action="" method="post" onsubmit="retrun checkUser();">
   <input type="text" name="username"  id="username" placeholder="用户名"/>
    <input type="password"  id="password" name="password"/>
     <input type="submit" name="submit" value="confirm"/>
</form>
</body>
 

谢谢大家😭😭😭

<head>
<meta charset="UTF-8">
<title>js</title>
<script type="text/javascript">
    function checkUser() {
        var username = document.getElementById("username").value;
        var password = document.getElementById("password").value;
        alert(username + "==" + password);
    }
</script>
</head>
<body>
    <form action="" method="post" onsubmit="checkUser()">
        <input type="text" name="username" id="username" placeholder="用户名" />
        <input type="password" id="password" name="password" /> <input
            type="submit" name="submit" value="confirm" />
    </form>
</body>

<head>
<meta charset="UTF-8">
<title>js</title>
<script type="text/javascript">
    function checkUser() {
        var username = document.getElementById("username").value;
        var password = document.getElementById("password").value;
        alert(username + "==" + password);
    }
</script>
</head>
<body>
    <form action="" method="post" onsubmit="checkUser();">
        <input type="text" name="username" id="username" placeholder="用户名" />
        <input type="password" id="password" name="password" /> <input
            type="submit" name="submit" value="confirm" />
    </form>
</body>