asp.net 的给文本框指定字符、（event.keyCode） javascript

指定text1文本框只能输入1234567;

 <form id="form1" runat="server">

    <div>
     <input  id="text1" type="text" onkeyup="checkinput('1234567',event)" />
    </div>

    </form>

<script type="text/javascript" >
      function checkinput(codes,e) {              //在火狐下的 、、
       
         var key1 = window.event ? e.keyCode : e.which;          //  火狐获取键盘 按下的 asc 码  
    
            for (var i = 0; i < codes.length; i++) {
                alert(codes.charCodeAt(i))
                  
            if (key1 == codes.charCodeAt(i)) {                            // codes.charCodeAt(i) 是取下表 为 i 的asc码
                return true;
                
            }
        }

        document.getElementById("text1").value = document.getElementById("text1").value.substr(0, document.getElementById("text1").value.length - 1);
       

        return false;
    }
 
    
</script>

 <script type="text/javascript">
                        function checkinput(codes) {
                            for (var i = 0; i < codes.length; i++) {
                            
                                if (event.keyCode == codes.charCodeAt(i)) {
                                    return true;
                                }
                            }
                           
                            document.getElementById("Text1").value = document.getElementById("Text1").value.substr(0, document.getElementById("Text1").value.length - 1);
                           
                            return false;
                        }

    </script>