<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> 

<form name=form1 action="" > 
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="23" 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>

<script type="text/javascript">
        var PasswordStrength ={
            Level : ["高，实在是高","还行啦","靠，这样也行"],
            LevelValue : [30,20,0],//强度值
            Factor : [1,2,5],//字符加数,分别为字母，数字，其它
            KindFactor : [0,0,10,20],//密码含几种组成的加数
            Regex : [/[a-zA-Z]/g,/d/g,/[^a-zA-Z0-9]/g] //字符正则数字正则其它正则
            }
        PasswordStrength.StrengthValue = function(pwd)
        {
            var strengthValue = 0;
            var ComposedKind = 0;
            for(var i = 0 ; i < this.Regex.length;i++)
            {
                var chars = pwd.match(this.Regex[i]);
                if(chars != null)
                {
                    strengthValue += chars.length * this.Factor[i];
                    ComposedKind ++;
                }
            }
            strengthValue += this.KindFactor[ComposedKind];
            return strengthValue;
        }
        PasswordStrength.StrengthLevel = function(pwd)
        {
            var value = this.StrengthValue(pwd);
            for(var i = 0 ; i < this.LevelValue.length ; i ++)
            {
                if(value >= this.LevelValue[i] )
                    return this.Level[i];
            }
        }
      
        alert(PasswordStrength.StrengthLevel("23"));
        alert(PasswordStrength.StrengthLevel("abcd123"));    
        alert(PasswordStrength.StrengthLevel("abcd!%23")); 
    </script>