```
/**
* @param {number[][]} grid
* @return {number}
*/
const islandPerimeter = function(grid) {
let island = 0;
let neighbour = 0;
let rows = grid.length;
let coloumns = grid[0].length;
for(let i = 0; i < rows; i += 1) {
for(let j = 0; j < coloumns; j += 1) {
if(grid[i][j] === 1) {
island += 1;
if(i < rows - 1 && grid[i + 1][j] === 1) {
neighbour += 1;
}
if(j < coloumns - 1 && grid[i][j + 1] === 1) {
neighbour += 1;
}
}
}
}
return 4 * island - 2 * neighbour;
};
```