JSFiddle - React, Tailwind, and code Playground

by Arvind Pal

JavaScript

var data = [
  [7, 9, 6, 7],
  [1, 3, 8, 5],
  [6, 2, 6, 7],
  [1, 3, 6, 8]
];

var a = 0,
  b = 0,
  final = 0;

function diagonal_sum_minus() {
  for (var i = 0; i < data.length; i++) {
    for (var j = 0; j < data[i].length; j++) {
      if (i === j) {
        a += data[i][j];
      }
      console.log(data[i].length - i)
      if ((data[i].length - 1 - i) === j) {
        b += data[i][j];
      }
    }
  }
}
diagonal_sum_minus();

alert(a - b)