push() method not working properly in JavaScript

Question

I'm trying to write a quite simple program that divides an array in another array of defined size smaller arrays, however the push() method is not working. Could someone please help me with it?

function chunk(array, size) {
  var newArray = [];
  var tempArray = [];

  for (let i = 0; i < array.length / size; i++) {
    for (let j = size * i, k = 0; j < size * i + size; j++, k++)
      tempArray[k] = array[j];

    newArray.push(tempArray);
  }

  return newArray;
}

var data = [1, 2, 3, 4, 5, 6, 7, 8];

console.log(chunk(data, 2));

The ideal output should be [[1, 2],[3, 4], [5, 6], [7, 8]]. However im getting [[7,8],[7,8],[7,8],[7,8]].

Answer 1

You're almost there. Just move the tempArray definition inside your first for-loop. Otherwise you would be pushing the same array each time.

Working Example:

function chunk(array, size) {
  const newArray = [];

  for (let i = 0; i < array.length / size; i++) {
    const tempArray = [];
    for (let j = size * i, k = 0; j < size * i + size; j++, k++)
      tempArray[k] = array[j];

    newArray.push(tempArray);
  }

  return newArray;
};

const data = [1, 2, 3, 4, 5, 6, 7, 8];

console.log(chunk(data, 2)); // [[1, 2],[3, 4], [5, 6], [7, 8]]

Answer 2

@Behemoth's answer is the correct one for the question. But if you want, you can take a slightly different approach like this to reach the solution as well.

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

var data = [1, 2, 3, 4, 5, 6, 7 ,8];

console.log(chunk(data, 2));

Answer 3

Slightly different solution than @Behemoth and @Rukshan

function chunk(array, size) {
  var newArray = [];
  var tempArray = [];

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

    for (let j = i; j < i + 1; j++) {
      for (let k = 0; k < size; k++) {
        if (array[size * j + k]) {
          tempArray.push(array[size * j + k]);
        }
      }
      newArray.push(tempArray);
      tempArray = [];
    }
  }
  return newArray;
};

var data = [1, 2, 3, 4, 5, 6, 7, 8];

console.log(chunk(data, 2));

The solution would be [ [ 1, 2 ], [ 3, 4 ], [ 5, 6 ], [ 7, 8 ], [ 9 ] ] instead of [ [ 1, 2 ], [ 3, 4 ], [ 5, 6 ], [ 7, 8 ]]