const FAIL = {};
let _pos;
let _input;

function parse(input) {
  _input = input;
  _pos = 0;
  const r = parens();
  if (r === FAIL || _pos !== _input.length) throw new Error('parse error');
  return r;
}

function parens() {
  let result = [];
  while (true) {
    const r = paren();
    if (r === FAIL) break;
    result.push(r);
  }
  return result;
}

function paren() {
  let r;
  r = p1();
  if (r !== FAIL) return r;
  r = p2();
  if (r !== FAIL) return r;
  return p3();
}

function p1() {
  const p = _pos; // parsing position 을 저장한다.
  let r;
  let result = [];
  r = char('(');
  if (r !== FAIL) {
    result.push(r);
    r = parens(); // 바로 여기 재귀 호출!
    if (r !== FAIL) {
      result.push(r);
      r = char(')');
      if (r !== FAIL) {
        result.push(r);
        return result;
      }
    }
  }
  _pos = p;
  return FAIL;
}

function p2() {
  const p = _pos; // parsing position 을 저장한다.
  let r;
  let result = [];
  r = char('[');
  if (r !== FAIL) {
    result.push(r);
    r = parens(); // 바로 여기 재귀 호출!
    if (r !== FAIL) {
      result.push(r);
      r = char(']');
      if (r !== FAIL) {
        result.push(r);
        return result;
      }
    }
  }
  _pos = p;
  return FAIL;
}

function p3() {
  const p = _pos; // parsing position 을 저장한다.
  let r;
  let result = [];
  r = char('{');
  if (r !== FAIL) {
    result.push(r);
    r = parens(); // 바로 여기 재귀 호출!
    if (r !== FAIL) {
      result.push(r);
      r = char('}');
      if (r !== FAIL) {
        result.push(r);
        return result;
      }
    }
  }
  _pos = p;
  return FAIL;
}

function char(c) {
  if (_pos < _input.length && _input[_pos] === c) {
    _pos++;
    return c;
  }
  return FAIL;
}

function long(nest) {
  let s = '';
  for (let i = 0; i < nest; i++) {
    s = '(' + s + ')';
  }
  return s;
}

console.log(parse(long(10000)));