# Counting Elements – LeetCode challenge JavaScript solution

Written on 9th Apr 2020

## Counting Elements Problem statement:

LeetCode

Given an integer array

``arr``
, count element
``x``
such that
``x + 1``
is also in
``arr``
.

If there’re duplicates in

``arr``
, count them separately.

Example 1:

```Input: arr = [1,2,3]
Output: 2
Explanation: 1 and 2 are counted cause 2 and 3 are in arr.```

Example 2:

```Input: arr = [1,1,3,3,5,5,7,7]
Output: 0
Explanation: No numbers are counted, cause there's no 2, 4, 6, or 8 in arr.
```

Example 3:

```Input: arr = [1,3,2,3,5,0]
Output: 3
Explanation: 0, 1 and 2 are counted cause 1, 2 and 3 are in arr.
```

Example 4:

```Input: arr = [1,1,2,2]
Output: 2
Explanation: Two 1s are counted cause 2 is in arr.
```

Constraints:

• ``1 <= arr.length <= 1000``
• ``0 <= arr[i] <= 1000``

## Counting Elements ES6 solution

```/**
* @param {number[]} arr
* @return {number}
*/
var countElements = function(arr) {
let count = 0;
for(let i = 0; i < arr.length; i++){
if(arr.includes(arr[i]+1))
count++;
}
}
return count;
};```

## Submission Output on LeetCode:

Rajesh-Royal on leetcode.