Merge Sort

merge_sort.js

let mergeSort = (arr) => {

  if (arr.length < 2) { 
    console.log("Merging len 1: ", arr);
    return arr;
  }

  console.log("Merging len > 1: ", arr)
  let mid = parseInt(arr.length / 2),
  l = arr.slice(0, mid),
  r = arr.slice(mid);
  console.log([mid, l, r]);

  return merge(mergeSort(l), mergeSort(r));
}

let merge = (l, r) => {
  let res = [];

  while (l.length && r.length) {
    l[0] <= r[0] ? res.push(l.shift()) : res.push(r.shift());
  }

  while (l.length) res.push(l.shift());
  while (r.length) res.push(r.shift());

  console.log("Merged: ", res);
  return res;
}
input = [3,4,5,6,1,2];
console.log(input);
output = mergeSort(input);
console.log(output);