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

So it looks like you want your username to have a "word" part (sequence of letters or numbers), interspersed with some "separator" part.

The regex will look something like this:

^[a-z0-9]+(?:[ _.-][a-z0-9]+)*$

Here's a schematic breakdown:

           _____sep-word…____
          /                  \
^[a-z0-9]+(?:[ _.-][a-z0-9]+)*$             i.e. "word ( sep word )*"
|\_______/   \____/\_______/  |
| "word"     "sep"   "word"   |
|                             |
from beginning of string...   till the end of string

So essentially we want to match things like word, word-sep-word, word-sep-word-sep-word, etc.

• There will be no consecutive sep without a word in between
• The first and last char will always be part of a word (i.e. not a sep char)

Note that for [ _.-], - is last so that it's not a range definition metacharacter. The (?:…) is what is called a non-capturing group. We need the brackets for grouping for the repetition (i.e. (…)*), but since we don't need the capture, we can use (?:…)* instead.

To allow uppercase/various Unicode letters etc, just expand the character class/use more flags as necessary.

References

• regular-expressions.info/Anchors, Character Class, Repetition, Grouping