My solution to - http://play.elevatorsaga.com/

elevator-saga-solution.js

{
    init: function(elevators, floors) {
        function getLeastBusyElevator(elevators) {            
            return elevators.reduce(function (currentLeast, thisElevator) {
                if (thisElevator.destinationQueue.length < currentLeast.destinationQueue.length &&
                    thisElevator.loadFactor() < 0.75
                ) {
                    return thisElevator;
                } else {
                    return currentLeast;
                }
            }, elevators[Math.floor(elevators.length * Math.random())]);
        }
        
        function elevatorAlreadyGoingToFloor(elevators, floorNum) {
            return elevators.some(function(elevator) {
                return elevator.inDestinationQueue(floorNum); 
            });
        }
        
        elevators.forEach(function (elevator) {
            elevator.inDestinationQueue = function(floorNum) {
                return elevator.destinationQueue.indexOf(floorNum) !== -1;
            }
            
            elevator.removeFromDestinationQueue = function(floorNum) {
                elevator.destinationQueue = elevator.destinationQueue.filter(function(item) { 
                    return item !== floorNum; 
                });
                elevator.checkDestinationQueue();
            }

            elevator.on("idle", function() {
                elevator.goingUpIndicator(true);
                elevator.goingDownIndicator(true);
            });
            
            elevator.on("floor_button_pressed", function(floorNum) {
                if (!elevator.inDestinationQueue(floorNum)) {
                    elevator.goToFloor(floorNum);
                }
            });

            elevator.on("passing_floor", function(floorNum, direction) {
                if (elevator.inDestinationQueue(floorNum)) {
                    elevator.removeFromDestinationQueue(floorNum);
                    elevator.goToFloor(floorNum, true);
                }
            });

            elevator.on("stopped_at_floor", function(floorNum) {
                if (elevator.loadFactor() > 0.5) {
                    switch (elevator.destinationDirection()) {
                        case "up":
                            elevator.goingUpIndicator(true);
                            elevator.goingDownIndicator(false);
                            break;
                        
                        case "down":
                            elevator.goingUpIndicator(false);
                            elevator.goingDownIndicator(true);
                            break;
                    }
                } else {
                    elevator.goingUpIndicator(true);
                    elevator.goingDownIndicator(true);
                }
            });
        });
        
        floors.forEach(function (floor) {
            floor.on("up_button_pressed down_button_pressed", function() {
                if (!elevatorAlreadyGoingToFloor(elevators, floor.floorNum())) {
                    getLeastBusyElevator(elevators).goToFloor(floor.floorNum());
                }
            });
        });
        
    },
    update: function(dt, elevators, floors) {
        // We normally don't need to do anything here
    }
}