Toeplitz Matrix

var isToeplitzMatrix = function (matrix) {
  let a = true;
  for (let i = 0; i < matrix.length; i++) {
    let j = 0;
    while (j + 1 < matrix[i].length && i + 1 < matrix.length) {
      if (matrix[i][j] !== matrix[i + 1][j + 1]) {
        a = false;
      }

      j++;
    }
  }

  return a;
};