1
/**
2
 * @param {number[]} nums
3
 * @return {number}
4
 */
5
var singleNumber = function (nums) {
6
  if (nums.length === 1) return nums[0];
7

8
  const objNums = {};
9
  for (var indexI = 0; indexI < nums.length; indexI++) {
10
    if (objNums[nums[indexI]] === 2) delete objNums[nums[indexI]];
11
    else objNums[nums[indexI]] = (objNums[nums[indexI]] || 0) + 1;
12
  }
13

14
  return Object.keys(objNums)[0];
15
};