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Rajesh Royal

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# Counting Elements – LeetCode challenge JavaScript solution

## 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;
};
``````