Count of pairs in an array that have consecutive numbers using JavaScript

Problem

We are required to write a JavaScript function that takes in an array of integers. Our function should return the count of such contagious pairs from the array that have consecutive numbers in them.

Example

Following is the code −

 Live Demo

const arr = [1, 2, 5, 8, -4, -3, 7, 6, 5];
const countPairs = (arr = []) => {
   let count = 0;
   for (var i=0; i<arr.length; i+=2){
      if(arr[i] - 1 === arr[i+1] || arr[i] + 1 === arr[i + 1]){
         count++;
      };
   };
   return count;
};
console.log(countPairs(arr));

Output

3