Code:

/**
 * @param {number[][]} grid
 * @return {number}
 */
var maxAreaOfIsland = function (grid) {
    const m = grid.length
    const n = grid[m - 1].length
    const visited = new Set()
    let max = 0

    const dfs = (i, j) => {
        if (i >= m || j >= n || i < 0 || j < 0 || grid[i][j] === 0 || visited.has(`${i}_${j}`)) {
            return 0
        }

        visited.add(`${i}_${j}`)        

        return grid[i][j] + dfs(i, j + 1) + dfs(i, j - 1) + dfs(i + 1, j) + dfs(i - 1, j)
    }

    for (let i = 0; i < m; i++) {
        for (let j = 0; j < n; j++) {
            if (grid[i][j] !== 0 && !visited.has(`${i}_${j}`)) {
                max = Math.max(max, dfs(i, j))
            }
        }
    }

    return max
};


console.log(maxAreaOfIsland([
    [0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0],
    [0, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 0, 0],
    [0, 1, 0, 0, 1, 1, 0, 0, 1, 1, 1, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0]
]))