Finite state machine is a very useful design model, it can be used to simulate many events in the world.In short, finite state machine has three features:Number of states is finiteAt any moment, one object can only be in one stateIn some condition, it will transfer from one state to another stateIn JavaScript, finite state machine can be applied in many places. For example, one menu element on a webpage. When the mouse hovers on the menu, the menu will show up, while the mouse moves away, the menu will hide. If we use a state machine, there are two states(show and hide), the mouse will trigger...