Is it possible to match different specific length using RegExp in JavaScript?

Question

I know that with JS RegExp I can match:

Exact length; /^[a-zA-Z]{7}$/
A length range; /^[a-zA-Z]{3,7}$/
A minimum length; /^[a-zA-Z]{3,}$/

What if I wanna match varying specific lengths? Something like: /^[a-zA-Z]{2|4|6}$/ meaning that the string must have either length of 2, 4 or 6 characters. Can I do it using JavaScript's RegExp?

I tried googling but couldn't find a way to search for this specific case, I always end up finding how to match length ranges.

Scenario: I currently have this if statement that I would like to make shorter:

if(typeof ean !== 'string' || !/^\d+$/.test(ean) || [8, 12, 13, 14].indexOf(ean.length) === -1) {
    return false;
}

Not sure if this helps stackoverflow.com/questions/12784338/… — j08691
– j08691, Commented Aug 21, 2014 at 22:29
No, regex won't let you match using a list like that. You could use ^[a-zA-Z]{2}(?:[a-zA-Z]{2}(?:[a-zA-Z]{2})?)?$ instead of an alternation. — user557597
– user557597, Commented Aug 21, 2014 at 23:24
If you're really trying to match lengths 2, 4, and 6, you could get clever and do /^(?:[a-zA-Z]{2}){1,3}$/. But this isn't a good, clean solution; it's a clever one. — David Ehrmann
– David Ehrmann, Commented Aug 21, 2014 at 23:49

voithos · Accepted Answer · 2014-08-21 22:25:04Z

3

All you need is the Regex OR | pattern, but it will require some repetition:

/^(?:[a-zA-Z]{2}|[a-zA-Z]{4}|[a-zA-Z]{6})$/

Note that the (?:...) part is just a non-capturing group, which is used to make all of the alternatives "act as one." Without it, the ^ and $ would have to be included in each alternative.

In your specific case, perhaps try:

/^(?:\d{8}|\d{12,14})$/

answered Aug 21, 2014 at 22:25

voithos

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