In Java regexes, you can use the intersection operator && in character classes to define them succinctly, e.g.
[a-z&&[def]] // d, e, or f
[a-z&&[^bc]] // a through z, except for b and c
Is there an equivalent in JavaScript?
4 Answers
Is there an equivalent in JavaScript?
Simple answer: no, there's not. It is specific Java syntax.
See: Regular Expressions Cookbook by Jan Goyvaerts and Steven Levithan. Here's a sneak-peek to the relevant section.
Probably needless to say, but the following JavaScript code:
if(s.match(/^[a-z]$/) && s.match(/[^bc]/)) { ... }
would do the same as the Java code:
if(s.matches("[a-z&&[^bc]]")) { ... }
Comments
As others have said, there isn't an equivalent, but you can achieve the effect of && using a look-ahead. The transformation is:
[classA&&classB]
becomes:
(?=classA)classB
For instance, this in Java:
[a-z&&[^bc]]
has the same behavior as this:
(?=[a-z])[^bc]
which is fully supported in JavaScript. I don't know the relative performance of the two forms (in engines like Java and Ruby that support both).
Since the && operator is commutative, you can always use either side for the (positive or negative) look-ahead part.
Intersection of a class with a negated class can also be implemented with negative look-ahead. So the example above could also have been transformed to:
(?![bc])[a-z]
Comments
2023 answer: Yes, there is.
With the v flag:
[[a-z]&&[def]]
[[a-z]&&[^bc]]
Try them on regex101.com.
You can also do subtraction: [[a-z]--[bc]]. More information can be found on MDN.
2 Comments
bobble bubble
It even works in my Opera. :D Still I'd hesitate to use this in production, better waiting some more years.
InSync
@bobblebubble Just like with any other new features in JS
:) Babel does have good support for v, however.You can get the same result as the Java regexes in JavaScript by writing out the character classes longhand, e.g.
Java JavaScript English
------------ ---------- -------
[a-z&&[def]] [def] d, e, or f
[a-z&&[^bc]] [ad-z] a through z, except for b and c
It’s just a bit more verbose/obscure in some circumstances, e.g.
Java JavaScript
---------------- -----------
[A-Z&&[^QVX]] [A-PR-UWYZ]
[A-Z&&[^CIKMOV]] [ABD-HJLNP-UW-Z]
[def]. Am I missing something? The second one makes sense (and is cool).'אבג'.match(/\w+/)match (i.e. no/uflag), and doesn't have\p{L}shorthand character classes. You can define them yourself, of course, but that isn't fun.