find number that appears only once

// array has numbers that appear twice, but not necessarily in order
// except one number will not appear twice
const nums = [0, 0, 1, 1, 2, 2, 3, 4, 4, 5, 5];

// faster
const getSingleNum = nums => {
  let pairs = {};

  nums.forEach(num =>
    pairs[num]
      ? (delete pairs[num])
      : (pairs[num] = true));

  return Object.keys(pairs)[0];
}

// slower
const getSingleNumOther = nums =>
  nums.find((num, i) =>
    !nums.some((otherNum, j) =>
      i !== j && num === otherNum
    )
  );