Regex Match only not keywords - regex

Question

I have a string like <dlskjfldjf>Text creation List<string> checking edit<br/>. Need help with regex to match only <dlskjfldjf> and not List<string>
Keyword could be any generic type like
IList<T>
List<T>
etc
I tried with <([a-zA-Z]+)> which would match <dlskjfldjf> and below which would match List<string> but not sure how to mix them both
((List|ilist|IList|IEnumerable|IQuerable)(<)([A-Za-z.,\[\]\s]*)(>))|(<T>)

Answer 1

Use a Zero-width negative lookbehind assertion (?<! expression ):
string pattern = #"(?<!(List|ilist|IList|IEnumerable|IQuerable))<([a-zA-Z]+)>";

Answer 2

In a language that supports Negative Lookbehind a pattern like this could work:
(?<!(List|ilist|IList|IEnumerable|IQuerable))<([a-zA-Z]+)>
In JavaScript you may need to use two patterns to achieve the same result, test once for the angle bracket pattern and then test again to ensure you don't have the type information preceding it.

Answer 3

What you could do is match what you don't want to keep, and capture in a group what you do want to keep:
\b(?:List|ilist|IList|IEnumerable|IQuerable)<[^<>]*>|(<[a-zA-Z]+>)
That will match:
\b Word boundary to prevent any of the listed words in the alternation being part of a larger word
(?: Non capturing group
List|ilist|IList|IEnumerable|IQuerable Alternation which will match any of the listed words
) Close non capturing group
<[^<>]*> Match <, not <> 0+ times, then matc >
| Or
( Capture group (What you want to keep)
<[a-zA-Z]+> Match <, then 1+ times a lower or uppercase char, then >
) Close capture group
For example:
const regex = /\b(?:List|ilist|IList|IEnumerable|IQuerable)<[^<>]*>|(<[a-zA-Z]+>)/g;
const str = `<dlskjfldjf>Text creation List<string> checking edit<br/> or IList<string> or <aAbB>`;
let m;
let res = [];
while ((m = regex.exec(str)) !== null) {
if (m.index === regex.lastIndex) {
regex.lastIndex++;
}
if (m[1] !== undefined) res.push(m[1]);
}
console.log(res);