Dividing the array into many subarrays where each subarray is of length chunk size

Question

I'm trying to divide an array into subarrays base on the length of the given size, I almost got it but the result has some issue.

[Array(2), empty, Array(2)] // I don't know why there's an empty field in array?
0: (2) [1, 2]
2: (2) [3, 4]

function chunks(array, size) {
  var chunk = new Array(size);

  for (let i = 0; i < array.length; i += size) {
    chunk[i] = array.slice(i, i + size);
  }

  return chunk;
}

console.log(chunks([1, 2, 3, 4], 2))

The output should be:

[[ 1, 2], [3, 4]]

Answer 1

You're skipping indices by using i += size (in your case, 2 comes after 0 so element at index 1 remains undefined), use an array literal [] and push:

function chunks(array, size) {
  var chunk = [];
  
  for (let i = 0; i < array.length; i += size) {
    chunk.push(array.slice(i, i + size));
  }
  
  return chunk;
}

console.log(chunks([1, 2, 3, 4], 2))

Or, use an additional index for the new array:

function chunks(array, size) {
  var chunk = [];
  
  for (let i = 0, j = 0; i < array.length; i += size, j++) {
    chunk[j] = array.slice(i, i + size);
  }
  
  return chunk;
}

console.log(chunks([1, 2, 3, 4], 2))

Answer 2

function chunks(array, size) {

  var chunk = new Array(Math.floor(array.length / size));
  var counter = -1;

  for (let i = 0; i < array.length; i += size) {

    chunk[++counter] = array.slice(i, i + size);
  }

  return chunk;
}

console.log(chunks([1, 2, 3, 4], 2))

when you skipped size with loop var i array index also skipped

Answer 3

function chunks(array, size) {

  var chunk = new Array(size);
  var index = 0;  // current index where we are going to insert value
  for (let i = 0; i <array.length; i+=size) {

    chunk[index] = array.slice(i,i+size);
    index++;
    // or you can do chunk.push(array.slice(i,i+size)); in one line
  }

  return chunk;
}

console.log(chunks([1, 2, 3, 4], 2))

Answer 4

function chunks(array, size) {
  if (!array.length || !parseInt(size)) {
    return array;
  }
  const isNeedOneMore = array.length % size > 0 ? 1 : 0;
  let chunksLength = (parseInt(array.length / size) + isNeedOneMore);
  let chunks = [];
  while (chunksLength > 0) {
    let chunk = [];
    let s = size;
    while (s > 0 && array.length > 0) {
      chunk.push(array.shift());
      s--;
    }
    chunks.push(chunk);
    chunksLength--;
  }
  return chunks;
}

console.log(chunks([1, 2, 3, 4], 2));