Javascript two dimensional array

let data = [];
for (let row=0; row<rows; row++) {
    data.push(new Array(cols).fill('#'));
};var x = new Array(10);

for (var i = 0; i < x.length; i++) {
  x[i] = new Array(3);
}

console.log(x);const fillSquareMatrix = (size) => {
  return Array(size)
    .fill()
    .map((u,y) => Array(size)
         .fill()
         .map((u,x) => y * size + x + 1));
};

console.log(fillSquareMatrix(3));//example of two dimensional array
var grid = [
  ["a", "b"],
  ["c", "d"],
  ["e", "f"]
];
console.log(grid[0][0]); // a
console.log(grid[1][1]); // d
console.log(grid);var grid = [];
iMax = 3;
jMax = 2;
count = 0;

    for (let i = 0; i < iMax; i++) {
      grid[i] = [];

      for (let j = 0; j < jMax; j++) {
        grid[i][j] = count;
        count++;
      }
    }

// grid = [
//   [ 0, 1 ]
//   [ 2, 3 ]
//   [ 4, 5 ]
// ];

console.log(grid[0][2]); // 4