Including a hyphen in a regex character bracket?

$.validator.addMethod('AZ09_', function (value) { 
    return /^[a-zA-Z0-9.-_]+$/.test(value); 
}, 'Only letters, numbers, and _-. are allowed');

When I use somehting like test-123 it still triggers as if the hyphen is invalid. I tried \- and --

Escaping using \- should be fine, but you can also try putting it at the beginning or the end of the character class. This should work for you:


Escaping the hyphen using \- is the correct way.

I have verified that the expression /^[a-zA-Z0-9.\-_]+$/ does allow hyphens. You can also use the \w class to shorten it to /^[\w.\-]+$/.

(Putting the hyphen last in the expression actually causes it to not require escaping, as it then can't be part of a range, however you might still want to get into the habit of always escaping it.)

\- should work to escape the - in the character range. Can you quote what you tested when it didn't seem to? Because it seems to work:

The \- maybe wasn't working because you passed the whole stuff from the server with a string. If that's the case, you should at first escape the \ so the server side program can handle it too.

  • In a server side string: \\-
  • On the client side: \-
  • In regex (covers): -

Or you can simply put at the and of the [] brackets.

A more generic way of matching hyphens is by using the character class for hyphens and dashes ("\p{Pd}" without quotes). If you are dealing with text from various cultures and sources, you might find that there are more types of hyphens out there, not just one character. You can add that inside the [] expression

Generally with hyphen (-) character in regex, its important to note the difference between escaping (\-) and not escaping (-) the hyphen because hyphen apart from being a character themselves are parsed to specify range in regex.

In the first case, with escaped hyphen (\-), regex will only match the hyphen as in example /^[+\-.]+$/

In the second case, not escaping for example /^[+-.]+$/ here since the hyphen is between plus and dot so it will match all characters with ASCII values between 43 (for plus) and 46 (for dot), so will include comma (ASCII value of 44) as a side-effect.