my solution for http://play.elevatorsaga.com/

elevator_2.js

{
  init: function(elevators, floors) {
    elevators.forEach(initElevator);
    floors.forEach(initFloor);

    var topFloor = floors.length - 1;
    
    function initElevator(elevator) {
      elevator.on("idle", function() {
      });

      elevator.on("stopped_at_floor", function(floorNum) {
        if (elevator.getPressedFloors().length === 0) {
          if(floorNum > 0) {
            elevator.destinationQueue = getFloorDownQueue();
            if (elevator.destinationQueue.length === 0) {
              elevator.destinationQueue = [0];
            }
            elevator.checkDestinationQueue();
            indicate('down');
          } else {
            elevator.destinationQueue = getFloorUpQueue();
            if (elevator.destinationQueue.length === 0) {
              elevator.destinationQueue = [topFloor];
            }
            elevator.checkDestinationQueue();
            indicate('up');
          }
        }
      });

      elevator.on("floor_button_pressed", function(floorNum) {
        if (elevator.destinationQueue.indexOf(floorNum) === -1) {
          elevator.destinationQueue.push(floorNum);
          elevator.destinationQueue.sort(function(a, b) {
            return (b - a) * (elevator.goingDownIndicator() ? 1 : -1);
          });
          elevator.checkDestinationQueue();
        }
      });
     
      function indicate(direction) {
        elevator.goingDownIndicator(direction === 'down');
        elevator.goingUpIndicator(direction === 'up');
      }
    }

    function initFloor(floor) {
      floor.on("up_button_pressed", function() {
        // Maybe tell an elevator to go to this floor?
      });
      floor.on("down_button_pressed", function() {
        // Maybe tell an elevator to go to this floor?
      });
    }

    function getFloorDownQueue() {
      return floors.reverse().filter(function(floor) {
        return !!floor.buttonStates.down;
        //https://github.com/magwo/elevatorsaga/issues/57
      }).map(function(floor) {
        return floor.floorNum();
      });
    }

    function getFloorUpQueue() {
      return floors.filter(function(floor) {
        return !!floor.buttonStates.up;
        //https://github.com/magwo/elevatorsaga/issues/57
      }).map(function(floor) {
        return floor.floorNum();
      });
    }


  },
  update: function(dt, elevators, floors) {
    // We normally don't need to do anything here
  }
}

elevator_5.js

{
  init: function(elevators, floors) {
    elevators.forEach(initElevator);
    floors.forEach(initFloor);

    var topFloor = floors.length - 1;
    var idleElevators = [];

    function initElevator(elevator, idx) {
      indicate('up');
      elevator.on("idle", function() {
        idleElevators.push(elevator);
      });

      elevator.on("stopped_at_floor", function(floorNum) {
        if (elevator.destinationQueue.length === 0) {
          elevator.destinationQueue = elevator.getPressedFloors();

          if(floorNum > 0) {
            indicate('down');
            elevator.destinationQueue = elevator.destinationQueue.concat(getFloorDownQueue());
            if (elevator.destinationQueue.length === 0) {
              elevator.destinationQueue = [0];
            }
          } else {
            indicate('up');
            elevator.destinationQueue = elevator.destinationQueue.concat(getFloorUpQueue());
            if (elevator.destinationQueue.length === 0) {
              elevator.destinationQueue = [topFloor];
            }
          }

          elevator.destinationQueue.sort(sortFloor);
          elevator.checkDestinationQueue();
          log(idx, elevator.goingDownIndicator()?'d':'u', elevator.loadFactor(), elevator.destinationQueue);
        }
      });

      elevator.on("floor_button_pressed", function(floorNum) {
        if (elevator.loadFactor() > 0.4) {
          elevator.destinationQueue = elevator.getPressedFloors();
        } else if (elevator.destinationQueue.indexOf(floorNum) === -1) {
          elevator.destinationQueue.push(floorNum);
        }
        elevator.destinationQueue.sort(sortFloor);
        elevator.checkDestinationQueue();
      });
     
      function indicate(direction) {
        elevator.goingDownIndicator(direction === 'down');
        elevator.goingUpIndicator(direction === 'up');
      }

      function sortFloor(a, b) {
        return (b - a) * (elevator.goingDownIndicator() ? 1 : -1);
      }
    }

    function initFloor(floor) {
      floor.on("up_button_pressed", function() {
        var elevator;
        if(elevator = idleElevators.pop()) {
          elevator.goToFloor(floor.floorNum());
        }
      });
      floor.on("down_button_pressed", function() {
        var elevator;
        if(elevator = idleElevators.pop()) {
          elevator.goToFloor(floor.floorNum());
        }
      });
    }

    function getFloorDownQueue() {
      return floors.reverse().filter(function(floor) {
        return !!floor.buttonStates.down;
        //https://github.com/magwo/elevatorsaga/issues/57
      }).map(function(floor) {
        return floor.floorNum();
      });
    }

    function getFloorUpQueue() {
      return floors.filter(function(floor) {
        return !!floor.buttonStates.up;
        //https://github.com/magwo/elevatorsaga/issues/57
      }).map(function(floor) {
        return floor.floorNum();
      });
    }


    function log(idx) {
      // if(idx === 0) {
        console.log.apply(console, arguments);
      // }
    }
  },
  update: function(dt, elevators, floors) {
    // We normally don't need to do anything here
  }
}