菜鸟求救,下面代码为什么实现不了表单的切换,求大神帮忙看看
<script type="text/javascript">
function displayForm(x) {
if(x="student"){
t =document.getElementById("teacher")
t.style.display="none";
s=document.getElementById("student")
s.style.display="";
} else{
s=document.getElementById("student")
s.style.display="none";
t =document.getElementById("teacher")
t.style.display="";
}
}
</script>
</head>
<body>
<SELECT onchange="displayForm(this.value)">
<option value="teacher" >老师登陆</option>
<option value="student">学生登陆</option>
</SELECT>
<div id="student" style=display:none>
<form action="student_login" method="post">
账号:<input type="text" name="student.username"/><br/>
密码: <input type="password" name="student.password"/><br/>
<input type="submit" value="登陆"/>
</form>
</div>
<div id="teacher" >
<form action="teacher_login" method="post">
工号:<input type="text" name="teacher.username"/><br/>
密码: <input type="password" name="teacher.password"/><br/>
<input type="submit" value="登陆"/>
</form>
</div>
</body>