merge-sort.js

function merge(a, b) {
  let i = 0;
  let j = 0;
  let k = 0;
  let arr = [];
  while (i < a.length && j < b.length) {
    if (a[i] <= b[j]) {
      arr[k] = a[i];
      i++;
    } else {
      arr[k] = b[j];
      j++;
    }
    k++;
  }
  while (i < a.length) {
    arr[k] = a[i];
    k++;
    i++;
  }
  while (j < b.length) {
    arr[k] = b[j];
    k++;
    j++;
  }
  console.log(`merge: ${arr}`);
  return arr;
}

function devide(a) {
  console.log(`devide: ${a}`);
  if (a.length == 1 || a.length == 0) {
    return a;
  }
  let leftArr = a.slice(0, Math.floor(a.length/2));
  let rightArr = a.slice(Math.floor(a.length/2), a.length);
  return merge(devide(leftArr), devide(rightArr));
}

console.log(`sorted: ${devide([])}`);