Example on handling "Back" button in Ludei/easeljs/typescript game

hardware.ts

declare var CocoonJS;
module hardware {
    var backButtonHandler: () => void = null;
    var backButtonDisplayObject: createjs.DisplayObject = null;

    /**
     * Call hardware.captureBackButton just before showing the screen, where you want to support "back" functionality,
     * pass your own handler (typically screen onQuit handler).
     *
     * It assumes that only one screen is shown at a time.
     *
     * Passed currentScreen display object is only used to check that screen object is indeed visible and
     * added to the stage. This call will be ignored (and default back button behavior will be used), if screen is hidden
     * or removed from stage. This may happen if user quit this screen using in-game UI (not back button). This is bit
     * hacky, but simplifies back button implementation in our simple usecase. 
     */
    export function captureBackButton(currentScreen: createjs.DisplayObject, handler: () => void) {
        backButtonDisplayObject = currentScreen;
        backButtonHandler = handler;
    }

    CocoonJS && CocoonJS.App.setAppShouldFinishCallback( () => {
        if (!backButtonHandler || !backButtonDisplayObject || !backButtonDisplayObject.getStage() || !backButtonDisplayObject.visible) {
            return true;
        }
        backButtonHandler();
        return false;
    })
}