密码强度验证

<script language="javascript" type="text/javascript">  
     //CharMode函数  
     //测试某个字符是属于哪一类.  
     function CharMode(iN){  
         if (iN>=48 && iN <=57) //数字  
         return 1;  
         if (iN>=65 && iN <=90) //大写字母  
         return 2;  
         if (iN>=97 && iN <=122) //小写  
         return 4;  
         else  
         return 8; //特殊字符  
     }  
     //bitTotal函数  
     //计算出当前密码当中一共有多少种模式  
     function bitTotal(num){  
         modes=0;  
         for (i=0;i<4;i++){  
         if (num & 1) modes++;  
         num>>>=1;  
         }  
         return modes;  
     }  
     //checkStrong函数  
     //返回密码的强度级别  

     function checkStrong(sPW){  
         if (sPW.length<=4)  
         return 0; //密码太短  
         Modes=0;  
         for (i=0;i<sPW.length;i++){  
         //测试每一个字符的类别并统计一共有多少种模式.  
         Modes|=CharMode(sPW.charCodeAt(i));  
         }  
         return bitTotal(Modes);  
     }  

     //pwStrength函数  
     //当用户放开键盘或密码输入框失去焦点时,根据不同的级别显示不同的颜色  
     function pwStrength(pwd){  
         O_color="#e0f0ff";  
         L_color="#FF0000";  
         M_color="#FF9900";  
         H_color="#33CC00";  
         if (pwd==null||pwd==''){  
             Lcolor=Mcolor=Hcolor=O_color;  
         }  
         else
         {  
             S_level=checkStrong(pwd);  
             switch(S_level)
             {  
                 case 0:  
                 Lcolor=Mcolor=Hcolor=O_color;  
                 case 1:  
                 Lcolor=L_color;  
                 Mcolor=Hcolor=O_color;  
                 break;  
                 case 2:  
                 Lcolor=Mcolor=M_color;  
                 Hcolor=O_color;  
                 break;  
                 default:  
                 Lcolor=Mcolor=Hcolor=H_color;  
             }  
         }  

         document.getElementById("strength_L").style.background=Lcolor;  
         document.getElementById("strength_M").style.background=Mcolor;  
         document.getElementById("strength_H").style.background=Hcolor;  
         return;  
     }  

</script>  

<form id="form1" runat="server">
     <div>
         输入密码:<asp:TextBox ID="TextBox1" runat="server" onKeyUp=pwStrength(this.value) onBlur=pwStrength(this.value) ></asp:TextBox><br />
         密码强度:
         <table border="1" cellpadding="1" borderColorDark="#fdfeff" borderColorLight="#99ccff" cellspacing="1" style="width: 200px; display: inline; background-color:#e0f0ff">
             <tr>
                 <td id="strength_L" style="width: 100px; height: 19px;" align="center">
                     弱</td>
                 <td id="strength_M" style="width: 100px; height: 19px;" align="center">
                     中</td>
                 <td id="strength_H" style="width: 100px; height: 19px;" align="center">
                     强</td>
             </tr>
         </table>
     </div>
     </form>