JS判断输入内容不能为中文

<script LANGUAGE="javascript">
function IsChar(s)
{
 var Number = "0123456789.abcdefghijklmnopqrstuvwxyz-\/ABCDEFGHIJKLMNOPQRSTUVWXYZ`~!@#$%^&*()_";
 for (i = 0; i < s.length;i++)
    {  
        // Check that current character isn't whitespace.
        var c = s.charAt(i);
        if (Number.indexOf(c) == -1) return false;
    }
 return true
}
function CheckChar(theField)
{
 if (!IsChar(theField.value))
  alert("该区域只能输入英文及数字，请不要输入中文！");
}
</script>

 
<input type=TEXT name="QTY<%=xuhao%>" value="<%=rs("num")%>" size=7 maxlength=20 onBlur="CheckChar(this)">