// Given an array, return an array of the top 2 most elements.
// Input: [1, 2, 3, 4, 5, 3, 4] | Output: [3, 4]
// Input: [2, 2, 3, 2, 4, 3, 4] | Output: [2,4]

const topTwoElement = nums => {
  const arr = [];
  nums.forEach(num => {
    arr[num] ? arr[num][1]++ : arr[num] = [num, 1];
  });

  arr.sort((a, b) => b[1] - a[1]);
  return [arr[0][0], arr[1][0]];
};

console.log(topTwoElement([3, 2, 3, 4, 5, 3, 4])); //[3,4]
console.log(topTwoElement([2, 2, 3, 2, 4, 3, 4])); //[2,4]