Classic Haskell quicksort to js es6 implementation with destructuring and rest/spread operator

quicksort.js

quickSort = ([x, ...xs]) => {
  if (typeof(x) === 'undefined') return [];
  return [
    ...quickSort(xs.filter(y => y <= x)),
    x,
    ...quickSort(xs.filter(y => y > x))
  ];
}