elevator crush saga

{
    init: function(elevators, floors) {
        //current #challenge=7
        var idleElevators = _.range(elevators.length);

        elevators.forEach(function(elevator, index) {
            elevator.index = index;
            elevator.on("idle", updateIdleQueue);
            elevator.on("floor_button_pressed", traverse);
            elevator.on("goto_floor", traverse);
        });
        
        floors.forEach(function(floor) {
            floor.on("up_button_pressed", function() {
                pickElevator(this.floorNum());
            });
            floor.on("down_button_pressed", function() {
                pickElevator(this.floorNum());
            });
        });
        
        function updateIdleQueue() {
            idleElevators.push(this.index);
        }
        
        function traverse(floorNum) {
            if(!_.contains(this.destinationQueue, floorNum)) {
                this.goToFloor(floorNum);
            }
        }
        
        function pickElevator(floorNum) {
            if(_.isEmpty(idleElevators)) return;
            var elevatorIndex = _.sample(idleElevators);
            _.pull(idleElevators, elevatorIndex);
            elevators[elevatorIndex].trigger("goto_floor", floorNum);
        }
    },
    update: function(dt, elevators, floors) {
        // We normally don't need to do anything here
    }
}