Check to see if a matrix is a Toeplitz matrix https://www.geeksforgeeks.org/find-if-given-matrix-is-toeplitz-or-not ES6

Toeplitz.js

#!/usr/bin/env node

// https://www.geeksforgeeks.org/find-if-given-matrix-is-toeplitz-or-not/

class Toeplitz {
  static check(matrix) {
    for (var i = 1; i < matrix.length - 1; i++) {
      let row = matrix[i]
      let prevRow = matrix[i - 1]
      for (var j = 1; j < row.length - 1; j++) {
        let diagonalParent = prevRow[j - 1]
        if (diagonalParent != row[j]) {
          return false
        }
      }
    }
    return true
  }
}

var isToe = [
  [6, 7, 8, 9],
  [4, 6, 7, 8],
  [1, 4, 6, 7],
  [0, 1, 4, 6],
  [2, 0, 1, 4]
]

console.log("Should be a Toeplitz:", Toeplitz.check(isToe))

var isNotToe = [
  [6, 7, 8, 9],
  [4, 6, 6, 8],
  [1, 2, 6, 7],
  [0, 1, 4, 6],
  [2, 8, 1, 4]
]

console.log("Should be a Toeplitz:", Toeplitz.check(isNotToe))