Merge Sort Algorithm

MergeSort.js

/*
  Merge Sort
*/

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

const merge = (left, right) => {
  const results = [];

  while (left.length && right.length) {
    if (left[0] <= right[0]) results.push(left.shift());
    else results.push(right.shift());
  }
  
  while(left.length) results.push(left.shift());
  while(right.length) results.push(right.shift());
  return results;
};