Mojo.Event.back

From WebOS101

This event is fired whenever the user does a back gesture (back swipe). You can react to this event to prevent popping your scene or to do additional cleanup before popping your scene.

StageAssistant.prototype.handleCommand = function (event) {
    if (event.type === Mojo.Event.back) {
        event.stop();
        event.stopPropagation();
        // Do some processing
        // Pop your current scene if needed
    }
};