Regex Optional char set in JavaScript

Question

I wanted to validate the Name data files with following condition

the Name contains digits 0 to 9, not all numeric
Name can contain hyphen -, provided that it is not the first or last character of the name
Name must contain 2 character, rest char are optional

So I tried the following Regex

    const regExp = /^[a-zA-Z0-9]+[a-zA-Z_-]+[a-zA-Z0-9]$/;

I need at least two characters, remaining are optional in the regExp everything works fine except this [a-zA-Z0-9] in the last, I want to make this optional

The "can't all be numeric" stipulation makes this a difficult regex. — Mordred
– Mordred, Commented Sep 5, 2019 at 15:30
Is 2-2 a valid name? If yes, then @WiktorStribiżew has the solution. — Mordred
– Mordred, Commented Sep 5, 2019 at 15:32
Then a better one is requiring a letter - /^(?=.{2})(?![^a-zA-Z]+$)[a-zA-Z0-9]+(?:[_-][a-zA-Z0-9]+)*$/ — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Sep 5, 2019 at 15:38

Wiktor Stribiżew · Accepted Answer · 2019-09-05 15:52:09Z

1

You may consider using

/^(?=.{2})(?![^a-zA-Z]+$)[a-zA-Z0-9]+(?:[_-][a-zA-Z0-9]+)*$/

See the regex demo

Details

^ - start of string
(?=.{2}) - at least two chars
(?![^a-zA-Z]+$) - the string can't have no ASCII letter
[a-zA-Z0-9]+ - 1+ ASCII alnum chars
(?:[_-][a-zA-Z0-9]+)* - 0 or more sequences of _ or - followed with 1+ ASCII alnum chars
$ - end of string.

answered Sep 5, 2019 at 15:52

Wiktor Stribiżew

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