[Algorithm] Chunk Array

// --- Directions
// Given an array and chunk size, divide the array into many subarrays
// where each subarray is of length size
// --- Examples
// chunk([1, 2, 3, 4], 2) --> [[ 1, 2], [3, 4]]
// chunk([1, 2, 3, 4, 5], 2) --> [[ 1, 2], [3, 4], [5]]
// chunk([1, 2, 3, 4, 5, 6, 7, 8], 3) --> [[ 1, 2, 3], [4, 5, 6], [7, 8]]
// chunk([1, 2, 3, 4, 5], 4) --> [[ 1, 2, 3, 4], [5]]
// chunk([1, 2, 3, 4, 5], 10) --> [[ 1, 2, 3, 4, 5]]

 

function chunk(array, size) {
  let result = [];
  let temp = [];
  const len = array.length;
  for (let i = 0; i < len; i++) {
    let mod = i % size;
    if (mod === 0) {
      if (temp.length !== 0) {
        result = [...result, temp];
      }
      temp = [];
    }

    temp[mod] = array[i];
  }

  result = [...result, temp];

  return result;
}

 

way 2:

function chunk(array, size) {
  let chunked = [];
  let index = 0;

  while (index < array.length) {
    chunked.push(array.slice(index, index + size));
    index += size;
  }

  return chunked;
}

 

test:

const chunk = require("./index");

test("function chunk exists", () => {
  expect(typeof chunk).toEqual("function");
});

test("chunk divides an array of 10 elements with chunk size 2", () => {
  const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
  const chunked = chunk(arr, 2);

  expect(chunked).toEqual([[1, 2], [3, 4], [5, 6], [7, 8], [9, 10]]);
});

test("chunk divides an array of 3 elements with chunk size 1", () => {
  const arr = [1, 2, 3];
  const chunked = chunk(arr, 1);

  expect(chunked).toEqual([[1], [2], [3]]);
});

test("chunk divides an array of 5 elements with chunk size 3", () => {
  const arr = [1, 2, 3, 4, 5];
  const chunked = chunk(arr, 3);

  expect(chunked).toEqual([[1, 2, 3], [4, 5]]);
});

test("chunk divides an array of 13 elements with chunk size 5", () => {
  const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13];
  const chunked = chunk(arr, 5);

  expect(chunked).toEqual([[1, 2, 3, 4, 5], [6, 7, 8, 9, 10], [11, 12, 13]]);
});