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;
};

Submission Output on LeetCode: