---
title: Diff Two Arrays
---
 Remember to use **`Read-Search-Ask`** if you get stuck. Try to pair program  and write your own code 
###  Problem Explanation:
Check two arrays and return a new array that contains only the items that are not in either of the original arrays.
#### Relevant Links
* for Loop (Devdocs)
* Array.prototype.includes (Devdocs)
* Array.prototype.filter (Devdocs)
* Array.prototype.concat (Devdocs)
##  Hint: 1
Merge the list to make it easy to compare functions.
> _try to solve the problem now_
##  Hint: 2
Use filter to get the new array, you will need to create a callback function.
> _try to solve the problem now_
##  Hint: 3
The best way to go about the callback function is to check if the number from the new merged array is not in **both** original arrays and return it.
> _try to solve the problem now_
## Spoiler Alert!
**Solution ahead!**
##  Basic Code Solution (Imperative Solution):
```javascript
function diffArray(arr1, arr2) {
var newArr = [];
function onlyInFirst(first, second) {
// Looping through an array to find elements that don't exist in another array
for (var i=0;iRun Code
### Code Explanation:
Read the comments in the code.
#### Relevant Links
* for Loop (Devdocs)
##  Intermediate Code Solution (Declarative Solution):
```javascript
function diffArray(arr1, arr2) {
return arr1
.concat(arr2)
.filter(
item => !arr1.includes(item) || !arr2.includes(item)
)
}
diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]);
```
 Run Code
### Code Explanation:
Explain solution here and add any relevant links
#### Relevant Links
* Array.prototype.concat (Devdocs)
* Array.prototype.filter (Devdocs)
* Array.prototype.includes (Devdocs)
##  Advanced Code Solution (Declarative Solution):
function diffArray(arr1, arr2) {
return arr1
.filter(el => !arr2.includes(el))
.concat(
arr2.filter(el => !arr1.includes(el))
)
}
diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]);
 Run Code
### Code Explanation:
Explain solution here and add any relevant links
##  Advanced Code Solution Alternative (Declarative Solution):
function diffArray(arr1, arr2) {
return [
...diff(arr1, arr2),
...diff(arr2, arr1)
]
function diff(a, b) {
return a.filter(item => b.indexOf(item) === -1);
}
}
#### Relevant Links
* Array.prototype.includes (Devdocs)
* Array.prototype.filter (Devdocs)
* Array.prototype.concat (Devdocs)
##  NOTES FOR CONTRIBUTIONS:
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