# 2 Uses of concat() method when working with arrays in JavaScript

Let's see two ways in which concat() method can be used while working with arrays in JavaScript. 

### 1) Merging two or more arrays

Let's now see how we can use the concat method to merge two given arrays, array 1 and array 2

```
const array1 = [1,2,3,4];
const array2 = [5,6,7];
// merge array 1 into array 2 and store it in a new variable 
const newMergedArray = [].concat(array1, array2);
console.log(newMergedArray); // [1, 2, 3, 4, 5, 6, 7]
console.log(array1); // [1, 2, 3, 4]
console.log(array2); // [5,6,7]
``` 

> const newMergedArray = [].concat(array1, array2);

In the above line [] creates a new array and the concat methods combine both array1, array2. This can also accept more than 2 arrays for concatenation by just adding them one next to the other

> const newMergedArray = [].concat(array1, array2, array 3, arrayN);

Another alternative for merging two arrays is below

> const newMergedArray = array1.concat(array2, array 3, arrayN);


### 2) Flatten single level nested arrays

Let's assume there is a nested array as below, and we would want to flatten it in such a way that the output is [1,2,3,4,5,6,7,8], this can be achieved by using concat() method with the help of spread operator.


```
const array1 = [1,2,[3,4],[5,6], 7, 8];
const flattened = [].concat(...array1);
console.log(flattened); // [1,2,3,4,5,6,7,8]
``` 
P.S. The above code flattens just a single-level nested array.


### References

-  [concat()](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/concat)  
-  [spread operator](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax) 


### Check out my other blog posts

-  [Getting Started with JavaScript - Ultimate Free Resources](https://blog.kritikapattalam.com/getting-started-with-javascript-ultimate-free-resources) 
-  [10 Things you can do in Chrome Developer Tools ](https://blog.kritikapattalam.com/10-things-you-can-do-in-chrome-developer-tools) 
-  [2 Simple ways you can truncate text using CSS](https://blog.kritikapattalam.com/2-simple-ways-you-can-truncate-text-using-css) 

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