Javascript Function Valid Username

Question

What's the best way/right way to create a javascript function that checks to see that the user has adhered to the valid character list below (user would enter a username through a html form) - if character list is adhered to function would return true - otherwise false.

validcharacters = '1234567890-_.abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';

Don't use loops and nested loops because it's not efficient. You have to use regular expressions. — Gabriel Llamas
– Gabriel Llamas, Commented Sep 7, 2011 at 9:09

Arnaud Le Blanc · Accepted Answer · 2011-09-07 09:47:52Z

15

function usernameIsValid(username) {
    return /^[0-9a-zA-Z_.-]+$/.test(username);
}

This function returns true if the regex matches. The regex matches if the username is composed only of number, letter and _, ., - characters.

You could also do it without regex:

function usernameIsValid(username) {
    var validcharacters = '1234567890-_.abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';

    for (var i = 0, l = username.length; i < l; ++i) {
        if (validcharacters.indexOf(username.substr(i, 1)) == -1) {
            return false;
        }
        return true;
    }
}

For this one, we iterate over all characters in username and verify that the character is in validcharacters.

edited Sep 7, 2011 at 9:47

answered Sep 7, 2011 at 9:08

Arnaud Le Blanc

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4 Comments

besamelsosu Over a year ago

could you explain use of !!, isn't it same with username.match(/^[0-9a-zA-Z_.-]+$/)?

Arnaud Le Blanc Over a year ago

The converts .match's return value to a boolean. See stackoverflow.com/questions/784929/…

sethobrien Over a year ago

Or do /^[0-9a-zA-Z_.\-]+$/.test(username). This may be a cheaper operation than match.

Sulung Nugroho Over a year ago

Can not remove the first char when backspace to revise?

Reporter · Accepted Answer · 2011-09-07 09:08:46Z

0

one way is to read each character from the input field and use the indexOf() function

answered Sep 7, 2011 at 9:08

Reporter

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