// https://www.freecodecamp.org/learn/coding-interview-prep/algorithms/find-the-symmetric-difference

function sym() {
  const symDiff = {};
  for (let [_, arr] of Object.entries(arguments)) {
    const set = {};
    arr.forEach((e) => {
      set[e] = true;
    });
    for (let [e, _] of Object.entries(set)) {
      if (symDiff[e]) {
        delete symDiff[e];
      } else {
        symDiff[e] = true;
      }
    }
  }
  return Object.keys(symDiff).map((e) => Number(e));
}

console.log(sym([1, 2, 3, 3], [5, 2, 1, 4]));