Merge Sort (JS)

merge-sort.js

const merge = (arr1, arr2) => {
  let sorted = [];

  while (arr1.length && arr2.length) {
    if (arr1[0] < arr2[0]) {
      sorted.push(arr1.shift());
    } else {
      sorted.push(arr2.shift());
    }
  }

  return [
    ...sorted,
    ...arr1,
    ...arr2
  ];
};

const mergeSort = arr => {
  if (arr.length <= 1) return arr;
  const mid = Math.floor(arr.length / 2);
  const left = mergeSort(arr.slice(0, mid));
  const right = mergeSort(arr.slice(mid));
  return merge(left, right);
};

const unsortedArr = [31, 99, 27, 28, 42, 13, 8, 11, 30, 17, 41, 15, 43, 1, 36, 9, 16, 20, 35, 48, 37, 7, 26, 34, 21, 22, 6, 29, 32, 49, 10, 12, 19, 24, 38, 5, 14, 44, 40, 3, 50, 46, 25, 18, 33, 47, 4, 45, 39, 23, 2];

console.log('sortedArr: ', mergeSort(unsortedArr));