Max Area of Island

let maxAreaOfIsland = function(grid) {

    if (!grid || !grid.length) return 0;

    let max = 0,
        maxRow = grid.length,
        maxCol = grid[0].length,
        LAND = 1, VISITED = 2;

    function markAndGetTotal(row, col) {
        if (row < 0 || row >= maxRow || col < 0 || col >= maxCol) return 0;
        if (grid[row][col] === LAND) {
            grid[row][col] = VISITED;

            let result = 1;
            // top
            result += markAndGetTotal(row - 1, col);
            // bottom
            result += markAndGetTotal(row + 1, col);
            // left
            result += markAndGetTotal(row, col - 1);
            /// right
            result += markAndGetTotal(row, col + 1);
            return result;
        }
        return 0;
    }

    for (let row = 0; row < maxRow;row++) {
        for (let col = 0; col < maxCol;col++) {
            if (grid[row][col] === LAND) {
                const total = markAndGetTotal(row, col); //?
                max = Math.max(total, max);
            }
        }
    }

    return max;
};