js判断密码强度

html代码：

 <form name="form1" action="">
     密码:<input type="password" size="8" onkeyup="pwStrength(this.value)" onblur="pwStrength(this.value)">
     <br>
     密码强度:
     <table width="220px" border="1" cellspacing="0" cellpadding="1" bordercolor="#eeeeee" height="22px">
         <tr align="center" bgcolor="#f5f5f5">
             <td width="33%" id="strength_L">弱</td>
             <td width="33%" id="strength_M">中</td>
             <td width="33%" id="strength_H">强</td>
         </tr>
     </table>
 </form>

js代码：

 function pwdStrength(pwd) {
     O_color = "#eeeeee";
     L_color = "#FF0000";
     M_color = "#FF9900";
     H_color = "#33CC00";
     var level = 0, strength = "O";
     if (pwd == null || pwd == '') {
         strength = "O";
         Lcolor = Mcolor = Hcolor = O_color;
     }
     else {
         var mode = 0;
         if (pwd.length <= 4)
             mode = 0;
         else {
             for (i = 0; i < pwd.length; i++) {
                 var charMode, charCode;
                 charCode = pwd.charCodeAt(i);
                 // 判断输入密码的类型
                 if (charCode >= 48 && charCode <= 57) //数字
                     charMode = 1;
                 else if (charCode >= 65 && charCode <= 90) //大写
                     charMode = 2;
                 else if (charCode >= 97 && charCode <= 122) //小写
                     charMode = 4;
                 else
                     charMode = 8;
                 mode |= charMode;
             }
             // 计算密码模式
             level = 0;
             for (i = 0; i < 4; i++) {
                 if (mode & 1)
                     level++;
                 mode >>>= 1;
             }
         }
         switch (level) {
             case 0:
                 strength = "O";
                 Lcolor = Mcolor = Hcolor = O_color;
                 break;
             case 1:
                 strength = "L";
                 Lcolor = L_color;
                 Mcolor = Hcolor = O_color;
                 break;
             case 2:
                 strength = "M";
                 Lcolor = Mcolor = M_color;
                 Hcolor = O_color;
                 break;
             default:
                 strength = "H";
                 Lcolor = Mcolor = Hcolor = H_color;
                 break;
         }
     }
     document.getElementById("strength_L").style.background = Lcolor;
     document.getElementById("strength_M").style.background = Mcolor;
     document.getElementById("strength_H").style.background = Hcolor;
     return strength;
 }