js判断密码强度

    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <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>>>=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="#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;
    return;
    }
    </script>
    </head>
    <body>

    <form name='from1' >
    输入密码:<input type='password' size='10' onKeyUp="pwStrength(this.value)" onBlur="pwStrength(this.value)" />
    <br/>密码强度:
    <table style='display:inline' >
    <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>

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