index.js

// quicksort an array, then map into li elements inside a ul

const ul = document.querySelector('ul');
const li = document.querySelectorAll('li');

const quicksort = (arr) => {
  if (arr.length <= 1) return arr;
  const pivot = arr[0];
  const left = [];
  const right = [];
  for (let i = 1; i < arr.length; i++) {
    if (arr[i] < pivot) {
      left.push(arr[i]);
    } else {
      right.push(arr[i]);
    }
  }
  return quicksort(left).concat(pivot, quicksort(right));
};

const sorted = quicksort(li);

const mapped = sorted.map(el => `<li>${el.textContent}</li>`);

ul.innerHTML = mapped.join('');