js(javascript)验证非法关键字

<script language="javascript" type="text/javascript">
var ss=/(上海)|(工开)|(阀门)/;//要屏蔽的关键字加到括号中，括号之间用竖线分隔
function ck(){
var kwd=form.kwd.value;
if (ss.test(kwd))
{
alert("内容含有非法字符！");
form.kwd.focus();
return false;
}
}
</script>
<form name="form" action="" onsubmit="return ck()">
<input type="test" name="kwd" />
<input type="submit" value=" submit " />
</form>