Question

I have created the following regex which matches either 9 consecutive numbers or 14 consecutive numbers.

^[0-9]{14}$|^[0-9]{9}$

How can I make this regex match 9 consecutive numbers or 14 consecutive numbers or null values?

Basically I want to modify the regex so that a user does not need to enter a value for this field. Or in other words making the validation for this field optional.

Answer 1

How about:

if (value.length && !value.match(/^(?:[0-9]{14}|[0-9]{9})$/) {
    alert('invalid value');
}

If string is empty, it will pass; if non-empty, it must match the regex.

Regex only solution:

if (!value.match(/^(?:[0-9]{14}|[0-9]{9})?$/) {
    alert('invalid value');
}