How to convert a PCRE2 regex to JavaScript? - regex

Question

This is the PCRE2 regexp:
(?<=hello )(?:[^_]\w++)++
It's intended use is against strings like the following:
Hello Bob (Marius) Smith. -> Match "Bob"
Hello Bob Jr. (Joseph) White -> Match "Bob Jr."
Hello Bob Jr. IInd (Paul) Jobs -> Match "Bob Jr. IInd"
You get the point.
Essentially there is a magic word, in this case "hello", followed by a first name, followed by a second name which is always between parens.
First names could be anything really. A single word, a list of words followed by punctuation, and so on. Heck, look at Elon Musks' kids' name (X Æ A-Xii) to see how weird names can get :)
Let's only assume ascii, though. Æ is not in my targets :)
I'm at a loss on how to convert this Regexp to JS, and the only viable solution I found was to use PCRE2-wasm on node which spins up a wasm virtual machine and sucks up 1gb of resources just for that. That's insane.

Answer 1

This would match your cases in ECMAscript.
(?<=[Hh]ello )(?:[^_][\w.]+)+
You need to look for a capital H done by looking for [Hh] instead of h, as your testcases starts with a capital H and your + needs to be single to be used in ECMAscript.
also you need to include a . with the \w since it is included in some names.
https://regex101.com/r/lkZK7w/1
-- thanks "D M" for pointing out the missing . in the testcase.

Answer 2

#Nils has the correct answer.
If you do need to expand your acceptable character set, you can use the following regex. Check it out. The g, m, and i flags are set.
(?<=hello ).*(?=\([^\)]*?\))
Hello Bob (Marius) Smith.
Hello Bob Jr. (Joseph) White
Hello Bob Jr. IInd (Paul) Jobs
Hello X Æ A-Xii (Not Elon) Musk
Hello Bob ()) Jr. ( (Darrell) Black
Match Number
Characters
Matched Text
Match 1
6-10
Bob
Match 2
32-40
Bob Jr.
Match 3
61-74
Bob Jr. IInd
Match 4
92-102
X Æ A-Xii
Match 5
124-138
Bob ()) Jr. (
The idea is pretty simple:
Look behind for your keyword: (?<=hello ).
Look ahead for your middle name: (?=\([^\)]*?\)) (anything inside a set of parenthesis that is not a closing parenthesis, lazily so you don't take part of the first name).
Take everything between as your first name: .*.

Answer 3

The ++ does not work as Javascript does not support possessive quantifiers.
As a first name, followed by a second name which is always between parens, you might also use a capture group with a match instead of a lookbehind.
\b[Hh]ello (\w+.*?)\s*\([^()\s]+\)
\b[Hh]ello Match hello or Hello
( Capture group 1
\w.*? Match 1+ word chars followed by any char as least as possible
) Close group 1
\s*\([^()\s]*\) Match optional whitespace char followed by ( till )
Regex demo
const regex = /\b[Hh]ello (\w+.*?)\s*\([^()\s]+\)/;
["Hello Bob (Marius) Smith.",
"Hello Bob Jr. (Joseph) White",
"Hello Bob Jr. IInd (Paul) Jobs"
].forEach(s => {
const m = s.match(regex);
if (m) {
console.log(m[1]);
}
})
With the lookbehind, you might also match word characters followed by an optionally repeated capture group matching whitspace chars followed by word characters or a dot.
(?<=[Hh]ello )\w+(?:\s+[\w.]+)*
Regex demo