findIndexOfMatchingParantheses.js

function isOpeningParantheses(char) {
  return char === "(" || char === "[" || char === "{" || char === "<";
}

function isClosingParantheses(char) {
  return char === ")" || char === "]" || char === "}" || char === ">";
}

function isParantheses(char) {
  return isOpeningParantheses(char) || isClosingParantheses(char);
}

const matchingParantheses = {
  "(": ")",
  ")": "(",
  "[": "]",
  "]": "[",
  "{": "}",
  "}": "{",
  "<": ">",
  ">": "<"
};
function isMatchingParantheses(p1, p2) {
  return matchingParantheses[p1] === p2 || matchingParantheses[p2] === p1;
}

function findIndexOfMatchingParantheses(str, paranthesesIndex) {
  if (!isParantheses(str[paranthesesIndex])) {
    throw new Error(
      `The character at the index ${paranthesesIndex} was not a parantheses, it was a ${str[paranthesesIndex]} instead!`
    );
  }

  const direction = isOpeningParantheses(str[paranthesesIndex])
    ? "RIGHT"
    : "LEFT";

  const stack = [];
  for (
    let idx = paranthesesIndex;
    idx >= 0 && idx < str.length;
    direction === "RIGHT" ? idx++ : idx--
  ) {
    let char = str[idx];

    if (isMatchingParantheses(char, stack[stack.length - 1])) {
      stack.pop();
    } else if (isParantheses(char)) {
      stack.push(char);
    }

    if (stack.length === 0) {
      return idx;
    }
  }

  return -1;
}

console.log(findIndexOfMatchingParantheses("a(b(), c(d(e[idx], f[idx])))", 1));
console.log(findIndexOfMatchingParantheses("a(b(), c(d(e[idx], f[idx])))", 3));
console.log(findIndexOfMatchingParantheses("a(b(), c(d(e[idx], f[idx])))", 8));
console.log(findIndexOfMatchingParantheses("a(b(), c(d(e[idx], f[idx])))", 12));

console.log(findIndexOfMatchingParantheses("a(b(), c(d(e[idx], f[idx])))", 27));
console.log(findIndexOfMatchingParantheses("a(b(), c(d(e[idx], f[idx])))", 4));
console.log(findIndexOfMatchingParantheses("a(b(), c(d(e[idx], f[idx])))", 26));
console.log(findIndexOfMatchingParantheses("a(b(), c(d(e[idx], f[idx])))", 16));

console.log(findIndexOfMatchingParantheses("(+ 2 (- 4 3) (+ 2 2))", 13));
console.log(findIndexOfMatchingParantheses("(+ 2 (- 4 3) (+ 2 2))", 19));

console.log(findIndexOfMatchingParantheses("new HelloWorld<Value>(5)", 14));
console.log(findIndexOfMatchingParantheses("new HelloWorld<Value>(5)", 20));

See: https://codesandbox.io/s/nifty-hill-ekrd3?file=/src/index.js:0-2380