Regex for username that allows numbers, letters and spaces

Question

I\'m looking for some regex code that I can use to check for a valid username.

I would like for the username to have letters (both upper case and lower case), number

Answer 1

You don't have to use a regex for everything. I find that requirements like the "no two consecutive characters" usually make the regexes so ugly that it's better to do that bit with a simple procedural loop.

I'd just use something like ^[A-Za-z0-9][A-Za-z0-9 \.\-_]*[A-Za-z0-9]$ (or the equivalents like ::alnum:: if your regex engine is more advanced) and then just check every character in a loop to make sure the next character isn't the same.

By doing it procedurally, you can check all the other rules you're likely to want at some point without resorting to what I call "regex gymnastics", things like:

• not allowed to contain your first or last name.
• no more than two consecutive digits.

and so forth.