Javascript hashmap

function zappa(nums) {
  const mapObj = new Map();
  for (let i = 0; i < nums.length; i++) {
     mapObj.set(nums[i], i);
  }
  return mapObj;
}
console.log(zappa([2, 7, 11, 15]));

function zappa(nums) {
  const mapObj = new Map();
  for (let i = 0; i < nums.length; i++) {
     mapObj.set(nums[i], i);
  }
  return mapObj;
}
console.log(zappa([2, 7, 11, 15]));

return mapObj.size
//console logs 4

return mapObj.size
//console logs 4