CheckTheGivenMatrixIsDiagonalOrNot.js

// Write a JavaScript program to check whether a matrix is a diagonal matrix or not. In linear algebra, a diagonal matrix is a matrix in which the entries outside the main diagonal are all zero (the diagonal from the upper left to the lower right).

// Example:
// [1, 0, 0], [0, 2, 0], [0, 0, 3] ]) = true
// [1, 0, 0], [0, 2, 3], [0, 0, 3] ]) = false

const prompt = require("prompt-sync")();

function isDiagonal(arr) {
  for (let i = 0; i < arr.length; i++) {
    for (let j = 0; j < arr.length; j++) {
      if (i !== j && arr[i][j] !== 0) {
        return false;
      }
    }
  }
  return true;
}

console.log("Enter the size of Diagonal Matrix : ");
var size = parseInt(prompt());

var arr = [];

for (let i = 0; i < size; i++) {
  arr[i] = [];
  for (let j = 0; j < size; j++) {
    console.log(`[${i}][${j}] : `);
    var elem = parseInt(prompt());
    arr[i][j] = elem;
  }
}

for (let i = 0; i < arr.length; i++) {
  for (let j = 0; j < arr.length; j++) {
    console.table(`[${i}][${j}] : ${arr[i][j]}\t`);
  }
}

var isTrue = isDiagonal(arr);
console.log(isTrue);