为什么setAttribute改变了值又回去了
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
table{
border-collapse: collapse;
}
</style>
<script>
function add() {
var tjbdd = document.getElementById("tjbd");
tjbdd.setAttribute("border", "10");
}
</script>
</head>
<body>
<form method="get" action="">
<table border="1"id="tjbd" >
<tr>
<td>ID</td>
<td>name</td>
<td>age</td>
<td>caozuo</td>
</tr>
</table>
<button onclick="add()">tianjia</button>
</form>
</body>
</html>