Quick Sort implemented in JavaScript

quick_sort.js

/* Quick sort is an efficient, recursive divide-and-conquer 
 * approach to sorting an array. In this method, a pivot value
 * is chosen in the original array. The array is then 
 * partitioned into two subarrays of values less than and 
 * greater than the pivot value. We then combine the result of
 * recursively calling the quick sort algorithm on both 
 * sub-arrays. This continues until the base case of an empty 
 * or single-item array is reached, which we return. The 
 * unwinding of the recursive calls return us the sorted array.
 */

const quickSort = array => {
  // Return the array if it's too short to sort
  if (array.length <= 1) {
    return array;
  }

  // Otherwise, make a clean copy of the array
  let arr = [...array];

  // Arbitrarily set last arr element as pivot value
  const pivot = arr.pop();

  // Make empty arrays for values <= and > pivot value
  const lessEq = [];
  const greater = [];

  // Loop through arr, separating values by comparison to pivot
  arr.forEach(n => (n <= pivot ? lessEq.push(n) : greater.push(n)));

  // Return recursively sorted values
  return [...quickSort(lessEq), pivot, ...quickSort(greater)];
};

const even = [3, 5, 2, 6, 1, 9];
const odd = [5, 8, 1, 9, 0, 7, 4];
const dups = [4, 4, 8, 2, 0, 1, 2, 9];

console.log('even:', quickSort(even)); // [ 1, 2, 3, 5, 6, 9 ]
console.log('odd:', quickSort(odd)); // [ 0, 1, 4, 5, 7, 8, 9 ]
console.log('dups:', quickSort(dups)); // [ 0, 1, 2, 2, 4, 4, 8, 9 ]