html中行內調用function的時候,是通過window調用的function，所以打印this等於打印window，所以在使用行內注冊事件時務必傳入參數this
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
<style>
.wrong {
border: 2px solid red;
}
.right {
border: 2px solid #91B81D;
}
</style>
</head>
<body>
賬號：<input type="text" name="name" value="" onblur="fn(this)" /><br /><br />
密碼：<input type="text" name="name" value="" onblur="fn(this)"/>
<script>
function fn(ele) {
if (ele.value.length < 6 || ele.value.length > 12) {
ele.className = "wrong";
} else {
ele.className = "right";
}
}
</script>
</body>
</html>
