Using regex to find deeply nested objects in Javascript source code

Question

I am currently refactoring my codebase to replace code like this:

one && one.two && one.two.three

with the equivalent using optional chaining:

one?.two?.three

but I'm having trouble coming up with a regular expression that matches instances of the former.

So far I've come up with this:

(([a-zA-Z0-9]*\.)*[a-zA-Z0-9]* && )+

which is OK but has a lot of false-positives (matching things like a && a.c && a.d.e && a.f.g.h)

The regex should match expressions of the form (any length):

one && one.two && one.two.three...
one.two && one.two.three && one.two.three.four...

But not match:

one && two...
one && two.three...

Any help is very much appreciated!

Maybe something along (\w+(?:\.\w+)*)\s*&&\s*(\1\.\w+)\s*&&\s*\2\.\w+ which will match condition chains with 3 elements. This will consequently also find larger chains but only match the first 3 elements. If you plan to replace them by hand, that should work anyways. — Sebastian Proske
– Sebastian Proske, Commented Jun 21, 2018 at 19:15
@SebastianProske excellent! If you convert to answer I'll gladly accept — wrymug
– wrymug, Commented Jun 21, 2018 at 19:27

Sebastian Proske · Accepted Answer · 2018-06-21 19:44:43Z

2

Seems you can make use of backreferences here and use

(\b\w+(?:\.\w+)*)\s*&&\s*(\1\.\w+)\s*&&\s*\2\.\w+

to match sequences of 3 elements as shown in your samples, where the first element is a sequence of dot separated words, the second is the first element + dot + another word and the third is the second element + dot + another word.

This will only match the first 3 elements if you have chains of 4 or more, but if you plan to do the replacements by hand, this shouldn't be a blocker.

See it in action here

edited Jun 21, 2018 at 19:44

answered Jun 21, 2018 at 19:36

Sebastian Proske

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