Split & stack an array into chunks

array_chunk.js

// Split & stack an array into chunks
// Ex: arrayChunk([1, 2, 3, 4, 5, 6, 8], 3) => [[1, 2, 3], [4, 5, 6], [7, 8]]

function arrayChunk (arr  = [], len = 2, stackRest = false) {
  const chunks = [];
  const n = arr.length;
  let i = 0;

  while (i < n) {
    const chunk = arr.slice(i, i += len);

    if (stackRest && chunk.length !== len) {
        chunks[chunks.length - 1].push(...chunk);
    } else {
        chunks.push(chunk);
    }
  }

  return chunks;
}