Given a square matrix of size N×N, calculate the absolute difference between the sums of its diagonals.

Diagonal_Difference.js

var a = [
  [1,2,3,5],
  [1,5,9,5],
  [1,5,0,8],
  [9,5,0,5]
]


    function diagonalsX() {
        var result = 0;
        a.forEach(function(item , i ,a) {
          result = result + item[i];
        })        
        
        return result;
    }
    
    function diagonalsY() {
        var result = 0;
        a.forEach(function(item , i ,a) {
          result = result + item[item.length - (i+1)]; 
        })        
        
        return result;
    }
    
            
console.log(Math.abs(diagonalsX() - diagonalsY()));