Merge sort

Definition

Merge sort is an efficient, general-purpose, comparison-based sorting algorithm. Merge sort is a divide and conquer algorithm, based on the idea of breaking down a array into several subarrays until each one consists of a single element and merging those subarrays in a manner that results into a sorted array.

Implementation

Use recursion.
If the length of the array is less than 2, return the array.
Use Math.floor() to calculate the middle point of the array.
Use Array.prototype.slice() to slice the array in two and recursively call mergeSort() on the created subarrays.
Finally, use Array.from() and Array.prototype.shift() to combine the two sorted subarrays into one.

const mergeSort = arr => {
  if (arr.length < 2) return arr;
  const mid = Math.floor(arr.length / 2);
  const l = mergeSort(arr.slice(0, mid));
  const r = mergeSort(arr.slice(mid, arr.length));
  return Array.from({ length: l.length + r.length }, () => {
    if (!l.length) return r.shift();
    else if (!r.length) return l.shift();
    else return l[0] > r[0] ? r.shift() : l.shift();
  });
};

mergeSort([5, 1, 4, 2, 3]); // [1, 2, 3, 4, 5]