Regex match in C# code but not in Jquery (MVC)

Question

My web application will generate the password on registration form. But user are allow to change password by it they want.

When user enter the password, it must follow our password policy.

Our password policy is :

The password length must be greater than or equal to 8
The password must contain one or more uppercase characters
The password must contain one or more lowercase characters
The password must contain one or more numeric values
The password must contain one or more special characters

The regex is (?=^.{8,}$)(?=.\d)(?=.[.!@#$%^&]+)(?![.\n])(?=.[A-Z])(?=.[a-z]).$

This is my C# code to generate password :

Regex passPattern = new Regex("(?=^.{8,}$)(?=.*\\d)(?=.*[!@#$%^&*]+)(?![.\n])(?=.*[A-Z])(?=.*[a-z]).*$");

    var password = System.Web.Security.Membership.GeneratePassword(10,2);

    while (true)
    {
    if (!passPattern.IsMatch(password))
       {
         password = System.Web.Security.Membership.GeneratePassword(10, 2);                                   
       }
       else
       {
        break;
       }    
    }

It will loop and keep generate the password until it match.

On the form, I also validate the password policy by using Jquery. Here the code snippet :

<script type="text/javascript">

$('#newPassword').keyup(function(e) {
    var strongRegex = new RegExp("(?=^.{8,}$)(?=.*\d)(?=.*[!@@#$%^&*]+)(?![.\n])(?=.*[A-Z])(?=.*[a-z]).*$", "g");       
    var enoughRegex = new RegExp("(?=.{8,}).*", "g");


    if (false == enoughRegex.test($(this).val())) {
        $('#passstrength').html('More Characters');
    }
    else if (strongRegex.test($(this).val())== true) {          
        $('#passstrength').html('Meet Our Password Policy!');
    }
    else {      
        $('#passstrength').html('Please insert strength password!');
    }

    return true;
});

So the result :

A%rI_2{l#Y = Not match
[email protected] = Match
2@C*DjDQdJ = Match
ex@#XcINQ0 = Not Match

As you see, not all the password is match. All this value have been tested at regex101.com & regexpal.com and all the result is match.

So how can solved this problem?

p/s: I using razor engine in my page, so you can see double '@' on my regex in jquery.

You have made at least 2 basic mistakes: 1) never use /g with RegExp.test() and 2) do not use a constructor notation when the pattern is known, use a literal regex notation (or you have to double backslashes) (that is, use var strongRegex = /^(?=.{8,}$)(?=.*\d)(?=.*[!@@#$%^&*]+)(?![.\n])(?=.*[A-Z])(?=.*[a-z]).*$/;). Instead of var enoughRegex = new RegExp("(?=.{8,}).*", "g");, you really could just check the password length. BTW, why use (?![.\n])? There seems to be no requirement Does not start with a dot or a line feed. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Feb 15, 2016 at 9:54
Does it really need to be regex? It would be much easier to implement and read without it (along with more informed errors why the password was invalid) — Sayse
– Sayse, Commented Feb 15, 2016 at 9:55
Why are you not just using a [RegularExpression] attribute applied to you model property so you get both client and server side validation out of the box without any of this code? — user3559349
– user3559349, Commented Feb 15, 2016 at 9:58
@StephenMuecke: Note that the validations are different on server and client side. That is also a good question, BTW. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Feb 15, 2016 at 9:59

Community · Accepted Answer · 2017-05-23 10:28:16Z

1

The problems with the code are:

/g modifier used in a regex that is later used in RegExp#test() (see this SO post)
single backslashes shorthand character classes in a constructor RegExp notation (see another post on this)

Also, note that checking the length of a string is better done with a regular string length check method:

$('#newPassword').keyup(function(e) {
    var strongRegex = /^(?=.*\d)(?=.*[!@@#$%^&*]+)(?![.\n])(?=.*[A-Z])(?=.*[a-z]).{8,}$/;       
    // Use the literal regex notation so as not to double escape \ symbols!  Else,
    // var strongRegex = RegExp("^(?=.*\\d)(?=.*[!@@#$%^&*]+)(?![.\n])(?=.*[A-Z])(?=.*[a-z]).{8,}$");
    if ($(this).val().length < 8) {   // no need in the enoughRegex
        $('#passstrength').html('More Characters');
    }
    else if (strongRegex.test($(this).val())) {          
        $('#passstrength').html('Meet Our Password Policy!');
    }
    else {      
        $('#passstrength').html('Please insert a strong password!');
    }

    return true;
});

edited May 23, 2017 at 10:28

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answered Feb 15, 2016 at 10:36

Wiktor Stribiżew

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2 Comments

Wiktor Stribiżew Over a year ago

I still am not sure what you want to express with (?![.\n]). Right now, it will mean Does not start with a dot or a line feed.

Azri Zakaria Over a year ago

Forgot to mention, our policy password is not allowed to put dot on first character. Just follow my boss instructions. No idea why. BTW, is working!

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