qsort.js

// from https://gist.github.com/zygygy/0feaff3f25ebe7e7e4dafa7b7f18c061

function partition(seq, pred) {
  const first = [];
  const second = [];
  seq.forEach(i => {
    if (pred(i)) {
      first.push(i);
    } else {
      second.push(i);
    }
  });
  return {
    first,
    second,
  }
}

function qsort(con) {
  if (!!!con || !!!con.length) {
    return [];
  }
  const head = con[0];
  const tail = con.slice(1);
  const comp = (v) => v < head;
  const {
    first: low,
    second: high,
  } = partition(tail, comp);
  return [].concat(
    qsort(low),
    [head],
    qsort(high)
  );
}

console.log(qsort([5,3,6,1,5,67,7,2]));