How Do I Detect Swamps in Screeps
Solution 1:
You can use Room.lookForAt method:
var terrain = creep.room.lookForAt('terrain', creep.pos.x+1, creep.pos.y);
if(terrain != 'swamp') {
creep.move(RIGHT);
}
If you want to find all terrain tiles from the entire room, check this SO question.