count the number of "islands" in an matrix of non-wraparound bits, where horizontally/vertically/diagonally adjacent bits are the same island

islands.js

const tests = [
    [0, [[0]]],
    [1, [[1]]],
    [1, [[1, 0], [0, 0]]],
    [1, [[0, 1], [0, 0]]],
    [1, [[0, 0], [1, 0]]],
    [1, [[0, 0], [0, 1]]],
    [1, [[1, 0], [0, 1]]],
    [1, [[0, 1], [0, 1]]],
    [1, [[1, 0], [1, 0]]],
    [1, [[0, 1], [1, 0]]],
    [1, [[1, 1], [1, 1]]],
    [2, [[0, 1, 0, 0], [0, 0, 1, 0], [1, 0, 0, 0], [0, 1, 0, 0]]],
    [16, [[0, 1, 0, 1, 0, 1, 0, 1],
          [0, 0, 0, 0, 0, 0, 0, 0],
          [0, 1, 0, 1, 0, 1, 0, 1],
          [0, 0, 0, 0, 0, 0, 0, 0],
          [0, 1, 0, 1, 0, 1, 0, 1],
          [0, 0, 0, 0, 0, 0, 0, 0],
          [0, 1, 0, 1, 0, 1, 0, 1],
          [0, 0, 0, 0, 0, 0, 0, 0]]]
].forEach(
    ([expected, map], i) =>
        console.assert(countIslands(map) == expected, `test ${i} failed`)
)

function countIslands(map) {
    const height = map.length
    const width = map[0].length
    var islands = 0

    for (let y = 0; y < height; y++) {
        for (let x = 0; x < width; x++) {
            if (map[y][x]) {
                if (!(map[y][x-1]
                      || ((y > 0) && 
                          (map[y-1][x-1] || map[y-1][x] || map[y-1][x+1])))) {
                    islands++
                }
            }
        }
    }

    return islands
}

exports = { countIslands }