QS code is from https://www.guru99.com/quicksort-in-javascript.html

is-quick-sort-fast.js

'use strict';

const quickSort = function (items, left, right) {
  let index;
  if (left === undefined) {
    left = 0;
  }
  if (right === undefined) {
    right = items.length - 1;
  }
  if (items.length > 1) {
    index = quickSort.partition(items, left, right); //index returned from partition
    if (left < index - 1) { //more elements on the left side of the pivot
      quickSort(items, left, index - 1);
    }
    if (index < right) { //more elements on the right side of the pivot
      quickSort(items, index, right);
    }
  }
  return items;
};

quickSort.partition = function (items, left, right) {
  const pivot = items[ Math.floor((right + left) / 2) ]; //middle element
  let i = left; //left pointer
  let j = right; //right pointer
  while (i <= j) {
    {
      while (items[i] < pivot) {
        i++;
      }
      while (items[j] > pivot) {
        j--;
      }
      if (i <= j) {
        quickSort.swap(items, i, j); //sawpping two elements
        i++;
        j--;
      }
    }
  }
  return i;
};

quickSort.swap = function (items, leftIndex, rightIndex) {
  const temp = items[leftIndex];
  items[leftIndex] = items[rightIndex];
  items[rightIndex] = temp;
};

// ============================

const checkOrder = function (arr) {
  let last = -Infinity;
  arr.forEach(each => {
    if (each < last) {
      throw new Error('wrong!');
    }
    last = each;
  });
};

const measure = function (func) {
  const begin = Date.now();
  func();
  console.log(`  Took: ${Date.now() - begin} milsec`);
};

const dupe = function (arr) {
  return JSON.parse(JSON.stringify(arr));
}

// ============================

const main = function () {
  const arr = [];
  for (let i = 0; i < 10000000; ++i) {
    arr.push( Math.round( Math.random() * 11 ) );
  }
  let q = dupe(arr);
  let b = dupe(arr);
  let prim = dupe(arr);

  // console.log(`orig: ${JSON.stringify(arr)}`);

  console.log('quick sort');
  measure(() => quickSort(q));

  console.log('builtin sort');
  measure(() => b.sort());

  console.log('primitive sort');
  measure(() => prim.sort((a, b) => {return (a === b) ? 0 : (a < b ? -1 : 1)}));

  // console.log(`orig: ${JSON.stringify(arr)}\nQuick: ${JSON.stringify(q)}\nBuilt-in: ${JSON.stringify(b)}\nPrimitive: ${JSON.stringify(prim)}`);

  if (JSON.stringify(q) !== JSON.stringify(b)) {
    console.log('builtin result is different');
  }

  if (JSON.stringify(q) !== JSON.stringify(prim)) {
    console.log('primitive result is different');
  }

  try {
    checkOrder(q)
  } catch (err) {
    console.log('quicksort did not pass');
  }
  try {
    checkOrder(b)
  } catch (err) {
    console.log('built-in sort did not pass');
  }
  try {
    checkOrder(prim)
  } catch (err) {
    console.log('primitive sort did not pass');
  }
};

// ============================

main();