Regex for matching everything inside a function curly braces

Question

I've found a lot of regex examples for matching content within nested brackets, but what I want to do is match:

a function with a particular name
match ALL content inside the curly braces (including any NESTED curly braces)

For example:

function someFunc() {
  const a = 6;

  if (a === 7) {
    while (true) {
      break;
    }
  }
}

This should find function someFunc+ignore anything up to first curly+then match all contents within the curly braces, including any nested braces.

I'm a noob at regex so I can't show you what I've done, I've been looking at Regex to get string between curly braces "{I want what's between the curly braces}" but none of them are suitable. Thanks!

PS expected output is a capture group of all contents within a function (which I can then replace).

Counting brackets is afaik too much to ask for regular expressions, unless you use exotic features that extend them past regular grammar's possibilities (which likely aren't there in javascript) — ASDFGerte, Mar 12 '18 at 15:57
It wasn't very clear for me what is the expected result for this input - could you clarify it? — arieljannai, Mar 12 '18 at 16:01
Something like this is better suited to using a parser. There are plenty of good parser engines out, eg. `https://pegjs.org/` In fact seen as it's Javascript your parsing, you could even use Babel, it has all the AST worked out for you. — Keith, Mar 12 '18 at 16:03
JS engine doesn't support recursions. So you can't do it in JS. — revo, Mar 12 '18 at 16:06
Regular expressions are only useful with [regular languages](https://en.wikipedia.org/wiki/Regular_language). JavaScript is [not a regular language](https://stackoverflow.com/questions/25247030/is-javascript-ecmascript-a-regular-language) — , Mar 12 '18 at 16:08
Thanks guys, I'll write it in plain old JS then! (or use a parser) — Dominic, Mar 12 '18 at 16:10
Would it be useful to take an oposite approach and REMOVE all un needed characters? In your description it looks like you just dont need `()` followed by a `{` at your function declaration... — Francis Leigh, Mar 12 '18 at 16:12
I would actually like to replace all the contents, so it should be `function someFunc() {}`. I will use some simple JS for this as it doesn't have to be resilient to strange function contents like strings with unmatched braces etc — Dominic, Mar 12 '18 at 16:15
If you have properly closed braces, you are lucky (even if it is difficult) - parsers work better than regexes. If there is an error in the code (improperly matched braces, even missing / extra braces), you may be out of luck. Please note that the word "function" may appear as a string inside the function (comment or fragment of keyword). Even smart parsers are sometimes bad at this, as far as I encountered. — virolino, Feb 12 '19 at 08:17

score 1 · Answer 1 · answered Mar 12 '18 at 16:32

1

Maybe this helps?

functionName\(.*{(.|\n)*}\n{2,}

this will search for a function called functionName followed by an open parenthesis and will get everything until it finds a closing curly bracket followed by two or more line breaks.

Here is a Regex101 to test it.

https://regex101.com/r/BadtRu/3

answered Mar 12 '18 at 16:32

R. Schifini

9,085
2
26
32

Thanks, there is only 1 line break after this function and I can't change that but good idea – Dominic Mar 12 '18 at 16:37
Are all functions followed by another? In that case add `function` at the end of the regexp (and remove `{2,}`) – R. Schifini Mar 12 '18 at 16:51
It is followed by another, but also inside there are three nested functions using the 'function' keyword – Dominic Mar 12 '18 at 17:13

score 0 · Answer 2 · answered Mar 12 '18 at 16:38

I've made a very naive function for this (because that's all I need as I know what the contents of the function looks like):

function loader(content, functionName) {
  // Find function
  const indexOfFunc = content.indexOf(`function ${functionName}`);

  if (indexOfFunc < 0) {
    return content;
  }

  const openingBrace = content.indexOf('{', indexOfFunc);

  // WARNING: We are assuming all braces in the function are balanced.
  // This won't be the case if there are braces in strings or comments
  // which aren't!
  const startPos = openingBrace + 1;
  let endPos = startPos;
  let bracesToBalance = 1;

  while (true) {
    if (content[endPos] === '{') {
      bracesToBalance++;
    } else if (content[endPos] === '}') {
      bracesToBalance--;
      if (bracesToBalance === 0) break;
    }
    endPos++;
  }

  return content.slice(0, startPos) + content.slice(endPos);
};

Regex for matching everything inside a function curly braces

2 Answers2