text: /************************************************************/
  /*Problem: Single Number  ********/
  /************************************************************/
  var singleNumber = function(nums) {
    let mapSingle = {};
    let single;
    for (let i = 0; i < nums.length; i++) {
      if(!mapSingle[nums[i]]) {
        const newItem = nums[i];
        mapSingle[newItem] = 'new';
      } else {
        const newItem = nums[i];
        mapSingle[newItem] = 'seen';
        //delete mapSingle[newItem];
      }
    }
    for (let i = 0; i < nums.length; i++) {
      if(mapSingle[nums[i]] === 'new') {
        return nums[i];
      } 
    }
    //return parseInt(Object.keys(mapSingle));
    //return mapSingle;
  };
  console.log(singleNumber([4,1,2,1,2]));
  console.log(singleNumber([2,2,1]));
  console.log(singleNumber([1,1,2,9,2,5,7,11,0,0,2,7,11,9,5]));
  console.log(singleNumber([4,1,2,1,2,4,0]));
  console.log(singleNumber([0,4,1,2,4,1,2,-1,0]));
  console.log(singleNumber([4,1,2,1,4,5,2]));