Treasure Island

(function main() {
  let grid = [['O', 'O', 'O', 'O'],
              ['D', 'O', 'D', 'O'],
              ['O', 'O', 'O', 'O'],
              ['O', 'D', 'D', 'D'],
              ['O', 'D', 'X', 'D'],
              ['O', 'D', 'O', 'D'],
              ['O', 'D', 'O', 'D'],
              ['O', 'O', 'O', 'O']];
  const minWithBFS = grid => {
    const isSafe = (x, y, grid) => grid[x] !== undefined && grid[x][y] !== undefined && grid[x][y] !== 'D';
    let steps = [[0,1], [0,-1], [1, 0], [-1, 0]];
    let visited = {};
    let Node = (x, y, step) => ({
      x,
      y,
      step: step,
      key: `${x}${y}`
    })
    let start = Node(0, 0, 0)
    let queue = [start];
    visited[start.key] = true
    while (queue.length > 0) {
      node = queue.pop();
      if (grid[node.x][node.y] === 'X') {
        return node.step;
      }
      steps.map(step => {
        next = Node(node.x + step[0], node.y + step[1], node.step + 1);
        if (visited[next.key] === undefined && isSafe(next.x, next.y, grid)) {
          queue.unshift(next);
          visited[next.key] = true;
        }
      })
    }
    return -1;
  }
  let min = minWithBFS(grid);
  console.log(min)
  return min;
}());