islandPerimeter with JavaScript

[nsaboo]

/**
 * @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;
};