JavaScript实现密码强度实时校验功能

<html>
<head>
<script language="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 /= 2;
 }
 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="#eeeeee";
 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;
}
</script>

</head>

<body>

<form>
输入密码:<input type="password" size="10" onKeyUp="pwStrength(this.value)" onBlur="pwStrength(this.value)">
<br>密码强度:
 <table width="217" border="1" cellspacing="0" cellpadding="1" bordercolor="#cccccc" height="20">
 <tr align="center" bgcolor="#eeeeee">
 <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>

</body>
</html>