Regex: parsing GitHub usernames (JavaScript)

Question

I am trying to parse GitHub usernames (which start with @) from a paragraph of text to associate them with related profiles.

GitHub username restrictions:

• Alphanumeric with single hyphens (without consecutive hyphens)
• You cannot start or end a hyphen (if it ends with a hyphen, just compare everything until then)
• Maximum length 39 characters.

---

For example, the following text:

Example @valid hello @ valid-username: @ another-valid-username, @ -invalid @ in-valid @ ignore-last-dash- [e-mail] @ another-valid?

script ...

Should match:

• @valid
• @ valid-username
• @ other-valid-username
• @in
• @ ignored last tier
• @

:

• @-
• [e-mail]

---

JavaScript, :

/\B@((?!.*(-){2,}.*)[a-z0-9][a-z0-9-]{0,38}[a-z0-9])/ig

(, @a).

: https://regex101.com/r/rZ5eW1/2

? ?

Answer 1

/\B@([a-z0-9](?:-?[a-z0-9]){0,38})/gi

. , (.. ., --), @ . OP , , . , ( ):

@abc.123
@abc--123
@abc-

, . Regex101 , :

• \B: " ", , , , , - [e-mail] . , ^[1] @reference.

  Honore Doktorr , lookbehind JS.

• @: @. , , .

• (...): . , , , @, , - .
• [a-z0-9]: . - i . , .
• (?:...): . , .
• -?[a-z0-9]: - , . , . , - - -, -, [a-z0-9].
• {0,38}: 0 38 , . # 4 39 . , , .

Answer 2

.

/\B@(?!.*(-){2,}.*)[a-z0-9](?:[a-z0-9-]{0,37}[a-z0-9])?\b/ig

. :

• (?!.*(-){2,}.*): , .
• [a-z0-9]: @ - .
• (?:[a-z0-9-]{0,37}[a-z0-9])?: 0-37 - , - , № 2 , , , . (?:…) .
• \b: break ( -).

Answer 3

RegEx, , github google ( ):

^@\w(-\w|\w\w|\w){0,19}$

:

• ^:
• @ -: .
• \w: [A-Za-z0-9_], , ( )
• $:
• {0,19}: , .

:

• RegEx ( ^ $)
• @, ( ), (@A, @1 @_)

• (...){0,19}:

  • \w (1- )
  • two \w (2nd opt)
  • \w ( )

  :

• :

• : @w-w
• : , , , - .
• 19 : 1- 2- 19*2=38 , 39 . , .

:

• @ww-w...w ( 39 ).
• @ww-w...w, 39 .

, ww-w w, , w ( 18 ), w- ( , 17, ), , 17 , 17*2=34. , 38 (34+2+1+1) , 39.

, , , RegEx . , javascript.