# How to find every element that exists in any of two given arrays once using JavaScript ?

In this article, we will learn how to find every element that exists in any of the given two arrays. To find every element that exists in any of two given arrays, you can merge the arrays and remove any duplicate elements.

## Method 1: Using Set

A set is a collection of unique items i.e. no element can be repeated. We will add all elements of two arrays to the set, and then we will return the set.

Example: In this example, we will see the use of the Javascript set method to find every element that exists in any of the two given arrays once.

## Javascript

 `// Function which takes an array as argument` `    ``const print = (arr1,arr2) => {` `    `  `        ``// Creating a set with elements of arr1` `        ``const set = ``new` `Set(arr1)` `    `  `        ``// Adding elements of arr2` `        ``arr2.forEach(element => {` `            ``set.add(element)` `        ``});` `    `  `        ``// Returning resultant array` `        ``return` `set` `    ``}` `    `  `    ``// Input array` `    ``const arr1 = [10, 20, 30, 40, 50]` `    ``const arr2 = [10,20,34,32,11]` `     `  `    ``// Printing the result` `    ``console.log(print(arr1,arr2))`

Output

```Set(8) { 10, 20, 30, 40, 50, 34, 32, 11 }

```

## Method 2: Using loop

In this approach, we will choose one array and then we will run a loop on the second array and check whether an element of this array is present in the first array or not. If an element is already present, we skip otherwise we will add this to the first array.

Example: In this example, we will see the use of Javascript loops to find every element that exists in any of the two given arrays once.

## Javascript

 `// Javascript program to find all element` `// present in any of two given arrays`   `// Function which takes an array as argument` `const print = (arr, arr2) => {`   `    ``// A counter for adding element` `    ``let k = arr.length`   `    ``// Checking every element and` `    ``// adding required element` `    ``arr2.forEach(element => {` `        ``if` `(arr.indexOf(element) == -1) {` `            ``arr[k] = element` `            ``k++` `        ``}` `    ``});`   `    ``// Returning resultant array` `    ``return` `arr` `}`   `// Input array` `const arr1 = [1, 2, 3, 4, 5]` `const arr2 = [1, 2, 3, 4]`   `// Printing the result` `console.log(print(arr1, arr2))`

Output

```[ 1, 2, 3, 4, 5 ]

```

## Method 3: Using filter() and concat()

In this method, we will use the concat() method to merge the array and filter() method for removing the element which repeats.

Example:

## Javascript

 `function` `findElementsInArr(arr1, arr2) {` `    ``let mergedArray = arr1.concat(arr2);` `    ``let uniqueEle = mergedArray.filter(``function` `(element, index, self) {` `        ``return` `self.indexOf(element) === index;` `    ``});` `    ``return` `uniqueEle;` `}`   `let arr1 = [1, 2, 3, 4];` `let arr2 = [3, 4, 5, 6];` `let result = findElementsInArr(arr1, arr2);` `console.log(result);`

Output

```[ 1, 2, 3, 4, 5, 6 ]

```

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