Recursive brace reversal

gistfile1.js

// foo(foo(bar))blim => foobaroofblim

function reverse(string) {
  return string
    .split('')
    .reverse()
    .join('');
}

function checkRecursion(input) {
  if (input.indexOf('(') > -1) {
    return reverseBraces(input, false);
  }

  if (input.indexOf(')') > -1) {
    return reverseBraces(input, false);
  }

  return input;
}

function reverseBraces(input, isFirstLevel = true) {
  // Grab the items outside of the two outer braces
  const [first] = input.split('(');
  const [last] = input.split(')').slice(-1);

  const result = checkRecursion(
    // Grab the area between the two outside braces
    input.slice(first.length + 1, input.length - last.length - 1),
  );

  // Entry to recursion we should not reverse the top level
  if (isFirstLevel) {
    return first + result + last;
  }

  // We should reverse the internal result and then reverse the whole result
  return reverse(first + reverse(result) + last);
}

console.log(reverseBraces('foo(foo(bar))blim'));