freeCodeCamp/guide/english/certifications/javascript-algorithms-and-data-structures/basic-algorithm-scripting/chunky-monkey/index.md

---
title: Chunky Monkey
---

# Chunky Monkey

---
## Problem Explanation

Our goal for this Algorithm is to split `arr` (first argument) into smaller chunks of arrays with the length provided by `size` (second argument). There are 4 green checks (objectives) our code needs to pass in order to complete this Algorithm:

1.  `(['a', 'b', 'c', 'd'], 2)` is expected to be `[['a', 'b'], ['c', 'd']]`
2.  `([0, 1, 2, 3, 4, 5], 3)` is expected to be `[[0, 1, 2], [3, 4, 5]]`
3.  `([0, 1, 2, 3, 4, 5], 2)` is expected to be `[[0, 1], [2, 3], [4, 5]]`
4.  `([0, 1, 2, 3, 4, 5], 4)` is expected to be `[[0, 1, 2, 3], [4, 5]]`

#### Relevant Links

*   <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/push' rel='nofollow'>Array.push()</a>
*   <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/slice' target='_blank' rel='nofollow'>Array.slice()</a>


---
## Hints

### Hint 1

The links above suggest to use `Array.push()`, so let's start by first creating a new array to store the smaller arrays we will soon have like this:

```javascript
var newArray = [];
```

### Hint 2

Next we'll need a `for loop` to loop through `arr`.

### Hint 3

Finally, we need a method to do the actual splitting and we can use `Array.slice()` to do that. The key to this Algorithm is understanding how a `for loop`, `size`, `Array.slice()` and `Array.push()` all work together.


---
## Solutions

<details><summary>Solution 1 (Click to Show/Hide)</summary>

```javascript
function chunkArrayInGroups(arr, size) {
  var temp = [];
  var result = [];

  for (var a = 0; a < arr.length; a++) {
    if (a % size !== size - 1) temp.push(arr[a]);
    else {
      temp.push(arr[a]);
      result.push(temp);
      temp = [];
    }
  }

  if (temp.length !== 0) result.push(temp);
  return result;
}
```

#### Code Explanation

*   Firstly, we create two empty arrays called `temp` and `result`, which we will eventually return.
*   Our **for loop** loops until `a` is equal to or more than the length of the array in our test.
*   Inside our loop, we push to `temp` using `temp.push(arr[a]);` if the remainder of `a / size` is not equal to `size - 1`.
*   Otherwise, we push to `temp`, push `temp` to the `result` variable and reset `temp` to an empty array.
*   Next, if `temp` isn't an empty array, we push it to `result`.
*   Finally, we return the value of `result`.

#### Relevant Links

*   <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/push' rel='nofollow'>Array.push()</a>
*   <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for' target='_blank' rel='nofollow'>For Loops</a>

</details>

<details><summary>Solution 2 (Click to Show/Hide)</summary>

```javascript
function chunkArrayInGroups(arr, size) {
  // Break it up.
  var arr2 = [];
  for (var i = 0; i < arr.length; i += size) {
    arr2.push(arr.slice(i, i + size));
  }
  return arr2;
}
```

#### Code Explanation

*   First, we create an empty array `arr2` where we will store our 'chunks'.
*   The for loop starts at zero, increments by `size` each time through the loop, and stops when it reaches `arr.length`.
*   Note that this for loop does not loop through `arr`. Instead, we are using the loop to generate numbers we can use as indices to slice the array in the right locations.
*   Inside our loop, we create each chunk using `arr.slice(i, i+size)`, and add this value to `arr2` with `arr2.push()`.
*   Finally, we return the value of `arr2`.

#### Relevant Links

*   <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/push' target='_blank' rel='nofollow'>Array.push()</a>
*   <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/slice' target='_blank' rel='nofollow'>Array.slice()</a>
*   <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for' target='_blank' rel='nofollow'>For Loops</a>

</details>

<details><summary>Solution 3 (Click to Show/Hide)</summary>

```javascript
function chunkArrayInGroups(arr, size) {
  // Break it up.
  var newArr = [];
  var i = 0;

  while (i < arr.length) {
    newArr.push(arr.slice(i, i + size));
    i += size;
  }
  return newArr;
}
chunkArrayInGroups(["a", "b", "c", "d"], 2);
```

#### Code Explanation

*   Firstly, we create two variables. `newArr` is an empty array which we will push to. We also have the `i` variable set to zero, for use in our while loop.
*   Our while loop loops until `i` is equal to or more than the length of the array in our test.
*   Inside our loop, we push to the `newArr` array using `arr.slice(i, i+size)`. For the first time it loops, it will look something like:

    newArr.push(arr.slice(1, 1+2))

*   After we push to `newArr`, we add the variable of `size` onto `i`.
*   Finally, we return the value of `newArr`.

#### Relevant Links

*   <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/push' target='_blank' rel='nofollow'>Array.push()</a>
*   <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/slice' target='_blank' rel='nofollow'>Array.slice()</a>
*   <a href='https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Statements/while' target='_blank' rel='nofollow'>While Loops</a>

</details>

<details><summary>Solution 4 (Click to Show/Hide)</summary>

```javascript
function chunkArrayInGroups(arr, size) {
  var newArr = [];
  while (arr.length) {
    newArr.push(arr.splice(0, size));
  }
  return newArr;
}
```

#### Code Explanation

*   Firstly, we create a variable. `newArr` is an empty array which we will push to.
*   Our `while` loop loops until the length of the array in our test is not 0.
*   Inside our loop, we push to the `newArr` array using `arr.splice(0, size)`.
*   For each iteration of `while` loop, it deletes `size` number of elements from the front of `arr` and push them as an array to `newArr`.
*   Finally, we return the value of `newArr`.

#### Relevant Links

*   <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/push' target='_blank' rel='nofollow'>Array.push()</a>
*   <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice' target='_blank' rel='nofollow'>Array.splice()</a>
*   <a href='https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Statements/while' target='_blank' rel='nofollow'>While Loops</a>

</details>

<details><summary>Solution 5 (Click to Show/Hide)</summary>

```javascript
function chunkArrayInGroups(arr, size) {
  if (arr.length <= size) {
    return [arr];
  } else {
    return [arr.slice(0, size)].concat(
      chunkArrayInGroups(arr.slice(size), size)
    );
  }
}
```

#### Code Explanation

* Array smaller than size is returned nested.
* For any array larger than size, it is split in two. First segment is nested and concatenated with second segment which makes a recursive call.

#### Relevant Links

*   <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Functions#Recursion' target='_blank' rel='nofollow'>Recursion</a>
*   <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/slice' target='_blank' rel='nofollow'>Array.slice()</a>
</details>