Question

My reg ex skills are almost zero and I am trying to match a field to have exactly 7 or 9 numbers (not between 7 or 9 so no 8 numbers is not valid).

I have tried (don’t laugh)

/^([0-9]{7} | [0-9]{9})

and

/^([0-9]{7 | 9})

if someone could help and explain the answer that would be much appreciated.

I assume (maybe incorrectly) that is does not matter what (programming) language I am using

Thanks

Answer 1

/^\d{7}(?:\d{2})?$/

\d is modern regex shorthand for [0-9], using (?: prevents a group capture you don’t want or need from happening.