I am aware this can easily be matched with /(\[tag\]|{{tag}})/ but that is not what I'm looking for. This is a beginning of a longer regex I'm trying to write (attribute parsing, etc.)
My criteria is:
I have the following regex working, but I am not comfortable with the regex not doing exactly as how you read it:
For the purposes of readability I am going to pretend that Javascript has the "X" flag here. I know that it doesn't.
(?:(\[)|{{) // Group with alternatives but only capturing group 1 so we can look around
(tag) // Capture the part between the wrappers
(?: // I don't care about capturing the closing wrapper, just match it
(?=\1)}} // Closing condition A (works, but why?)
| // OR
(?!\1)] // Closing condition B (works, but why?)
)
As you can see it works here:
let input = `
[tag][ <--
[tag[
[tag}}
{{tag]
{{tag}} <--
tag}}
{{tag
[tag
tag]
`;
input = input.replace(/(?:(\[)|{{)(tag)((?=\1)}}|(?!\1)])/g, "@@@@@");
console.log(input);If I try to eye-parse the regex, shouldn't it be that closing condition A need to match ] when \k<s> is true?
However, if I do that I end up matching the wrong things and only the above configuration works.
Any regex gurus want to illuminate me?
Thanks, voldomazta
The first match will use closing condition B because the next char is ], which isn't \1.
The second match will use closing condition A because group 1 is undefined, which will satisfy the look ahead.
Since javascript regex doesn't support conditionals (like C# does), I would go for the pattern you have in first line. However, to only have the tag part once, I would write tag regex part in a variable, then use the constructor that takes a string, now it's easy to add the same string twice and you only have one regex to maintain.