In a regular expression, match one thing or another, or both

Question

In a regular expression, I need to know how to match one thing or another, or both (in order). But at least one of the things needs to be there.

For example, the fol

Answer 1

Yes, you can match all of these with such an expression:

/^[0-9]*\.?[0-9]+$/

Note, it also doesn't match the empty string (your last condition).