---
id: 587d7da9367417b2b2512b66
title: Combine Two Arrays Using the concat Method
challengeType: 1
---
## Description
Concatenation means to join items end to end. JavaScript offers the concat method for both strings and arrays that work in the same way. For arrays, the method is called on one, then another array is provided as the argument to concat, which is added to the end of the first array. It returns a new array and does not mutate either of the original arrays. Here's an example:
[1, 2, 3].concat([4, 5, 6]);
// Returns a new array [1, 2, 3, 4, 5, 6]
## Instructions
Use the concat method in the nonMutatingConcat function to concatenate attach to the end of original. The function should return the concatenated array.
## Tests
```yml
tests:
- text: Your code should use the concat method.
testString: assert(code.match(/\.concat/g), 'Your code should use the concat method.');
- text: The first array should not change.
testString: assert(JSON.stringify(first) === JSON.stringify([1, 2, 3]), 'The first array should not change.');
- text: The second array should not change.
testString: assert(JSON.stringify(second) === JSON.stringify([4, 5]), 'The second array should not change.');
- text: nonMutatingConcat([1, 2, 3], [4, 5]) should return [1, 2, 3, 4, 5].
testString: assert(JSON.stringify(nonMutatingConcat([1, 2, 3], [4, 5])) === JSON.stringify([1, 2, 3, 4, 5]), 'nonMutatingConcat([1, 2, 3], [4, 5]) should return [1, 2, 3, 4, 5].');
```
## Challenge Seed
```js
function nonMutatingConcat(original, attach) {
// Add your code below this line
// Add your code above this line
}
var first = [1, 2, 3];
var second = [4, 5];
nonMutatingConcat(first, second);
```
## Solution
```js
// solution required
```