pos.js

[...]
  // Reverse of parseRoomName
  renderRoomName(room) {
    if (room[0] === 255) {
      return 'sim';
    }
    return (
      (room[0] < 0 ? 'W'+ (-room[0] - 1) : 'E'+ room[0])+
      (room[1] < 0 ? 'N'+ (-room[1] - 1) : 'S'+ room[1])
    );
  },


[....]
  // Return world offset from origin
  parseRoomName() {
    if (this.roomName === 'sim') {
      return [255, 255];
    } else {
      let room = /^([WE])([0-9]+)([NS])([0-9]+)$/.exec(this.roomName);
      if (!room) {
        throw new Error('Invalid room name');
      }
      return [
        room[1] === 'W' ? -room[2] - 1 : +room[2],
        room[3] === 'N' ? -room[4] - 1 : +room[4],
      ];
    }
  },