JavaScript获取网页支持表单字符集的方法

<!DOCTYPE html>
<html>
<body>
<form id="frm1" accept-charset="ISO-8859-1">
First name: <input type="text" name="fname" value="Donald"><br>
Last name: <input type="text" name="lname" value="Duck"><br>
</form>
<p>The value of the accept-charset attribute is:
<script>
document.write(document.getElementById("frm1").acceptCharset)
</script>
</p>
</body>
</html>

The value of the accept-charset attribute is:ISO-8859-1