766. Toeplitz Matrix

Question:

A matrix is Toeplitz if every diagonal from top-left to bottom-right has the same element.
Now given an M x N matrix, return True if and only if the matrix is Toeplitz.

如果从左上角到右下角的每个对角线具有相同的元素，则矩阵是Toeplitz。
现在给出一个Mxn矩阵，当且仅当矩阵是Toeplitz时返回真。

Example:

Input:
    matrix = [
      [1,2,3,4],
      [5,1,2,3],
      [9,5,1,2]
    ]
Output: 
    True
Explanation:
    In the above grid, the diagonals are:
    "[9]", "[5, 5]", "[1, 1, 1]", "[2, 2, 2]", "[3, 3]", "[4]".
    In each diagonal all elements are the same, so the answer is True.

Input:
    matrix = [
      [1,2],
      [2,2]
    ]
Output: 
    False
Explanation:
    The diagonal "[1, 2]" has different elements.

Solution:

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