463. Island Perimeter

/**
 * @param {number[][]} grid
 * @return {number}
 */
var islandPerimeter = function(grid) {
    const rows = grid.length
    const cols = grid[0].length
    let perimeter  = 0

    const isWater = (r, c) => {
        return r < 0 || r >= rows || c < 0 || c >= cols || grid[r][c] === 0
    }

    for (let r = 0; r < rows; r++) {
        for (let c = 0; c < cols; c++) {
            if (grid[r][c] === 1) {
                if (isWater(r - 1, c)) perimeter++
                if (isWater(r + 1, c)) perimeter++
                if (isWater(r, c - 1)) perimeter++
                if (isWater(r, c + 1)) perimeter++
            }
        }
    }

    return perimeter

};