Use Javascript to evaluate the strength of the password entered by the user

Passwords have become an indispensable tool in our lives and work, but an unsafe password may cause us unnecessary losses. As website designers, if we can conduct a security assessment on the password entered by the user on the web page and display the corresponding prompt information, it will be of great help to the user to set a secure password. At the same time, it also makes the website more user-friendly and attractive.
What is a secure password? This program evaluates it in the following way.
1. If the password is less than 5 characters, it is considered a weak password.
2. If the password only consists of one of numbers, lowercase letters, uppercase letters or other special symbols, it is considered a weak password.
3. If the password consists of two types of numbers, lowercase letters, uppercase letters or other special symbols, it is considered a moderately secure password.
4. If the password consists of more than three types of numbers, lowercase letters, uppercase letters or other special symbols, it is considered a relatively secure password.

The specific program is as follows (demo address: http://www.netInter.cn/reg):

<script language=javascript>

//Program design: Global Wanwei, specializing in domain name registration and virtual hosting services
//Website: http://www.netInter.cn
//This program is an original program of Global Wanwei. If you need to reprint it, please indicate the URL and source. Thank you.
//The above information is an integral part of the article text, so if you want to reprint this article, you must retain the above information.

//CharMode function
//Test which category a character belongs to.
function CharMode(iN){
if (iN>=48 && iN <=57) //number
return 1;
if (iN>=65 && iN <=90) //uppercase letters
return 2;
if (iN>=97 && iN <=122) //lowercase
return 4;
else
return 8; //Special characters
}

//bitTotal function
//Calculate how many modes there are in the current password
function bitTotal(num){
modes=0;
for (i=0;i<4;i++){
if (num & 1) modes++;
num>>>=1;
}
return modes;
}

//checkStrong function
//Return the password strength level

function checkStrong(sPW){
if (sPW.length<=4)
return 0; //Password is too short
Modes=0;
for (i=0;i<sPW.length;i++){
//Test the category of each character and count how many patterns there are.
Modes|=CharMode(sPW.charCodeAt(i));
}

return bitTotal(Modes);

}

//pwStrength function
//When the user releases the keyboard or the password input box loses focus, different colors are displayed according to different levels

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="" >
Enter password:<input type=password size=10 onKeyUp=pwStrength(this.value) onBlur=pwStrength(this.value)>
<br>Password Strength:
<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">Weak</td>

<td width="33%" id="strength_M">Medium</ td>

<td width="33%" id="strength_H">Strong</td>
</tr>
</table>

</form>