Chunk array

chunk.js

function chunk(array, size) {
  if (!array) return [];
  const firstChunk = array.slice(0, size); // create the first chunk of the given array
  if (!firstChunk.length) {
    return array; // this is the base case to terminal the recursive
  }
  return [firstChunk].concat(chunk(array.slice(size, array.length), size)); 
}

/*
Let's take an example to make it more easy to understand
chunk([1, 2, 3, 4], 2);

1st call - chunk([1,2 3,4], 2) = [[1,2]].concat(chunk([3,4], 2));
2nd call - chunk([3, 4], 2) = [[3 ,4]].concat(chunk([], 2));
3rd call - chunk([], 2) = [] //base case

so basically, chunk([1, 2, 3, 4], 2) = [[1,2]].concat([[3 ,4]].concat([])) = [[1,2], [3, 4]]

*/