SwitchHub is a finite state machine written for JavaScript. It can help you manage the state of an object declaratively. It can determine and transition to its future state by looking at its current state and your actions. Also, it can undo and redo transitions.
You can use npm to install this library.
npm install --save switchhub
To create an instance and register a list of states and events.
import{StateMachine}from'switchhub';conststateMachine=StateMachine.create('inactive');stateMachine.addEvent('activate',[{from:'inactive',to:'active'},]);stateMachine.addEvent('deactivate',[{from:'active',to:'inactive'},{from:'paused',to:'inactive'},]);stateMachine.addEvent('pause',[{from:'active',to:'paused'},]);stateMachine.addEvent('resume',[{from:'paused',to:'active'},]);You can also add a transition without an event.
stateMachine.addTransition({from:'inactive',to:'active'});If you want to make a transition conditional, you can add acondition property to it.
letcanPause=false;stateMachine.addEvent('pause',[{from:'active',to:'paused',condition:()=>canPause},// `condition` function should return true or false]);To transition to a new state by triggering an event.
// Given the initial state is 'inactive'stateMachine.triggerEvent('activate');// stateMachine.getState() === 'active'stateMachine.triggerEvent('pause');// stateMachine.getState() === 'paused'stateMachine.triggerEvent('deactivate');// stateMachine.getState() === 'inactive'You can also directly transition to a new state, if it is related to the current state.
// Given the current state is 'inactive', you can transition to 'active'stateMachine.transition('active');// stateMachine.getState() === 'active'// Given the current state is 'paused', you cannot transition to 'inactive'stateMachine.transition('inactive');// stateMachine.getState() !== 'inactive'You can optionally pass meta data to subscribers when you transition to a new state.
stateMachine.subscribe(transition)=>{// transition.data.message === 'Hello world'});stateMachine.triggerEvent('activate',{message:'Hello world'});You can undo / redo a transition if it is marked as undoable.
stateMachine.addEvent('activate',[{from:'inactive',to:'active',undoable:true},]);stateMachine.triggerEvent('activate');stateMachine.undoTransition();stateMachine.redoTransition();When passing data totriggerEvent ortransition, make sure it is immutable. Otherwise, when you redo a transition, your subscribers might not get the same value.
You can subscribe to state changes.
stateMachine.subscribe(transition=>{// transition.event === 'activate'// transition.from === 'inactive'// transition.to === 'active'});stateMachine.subscribe(transition=>{// You can have more than one subscriber});stateMachine.transition('activate');To remove an event, transition or subscriber.
stateMachine.removeEvent('pause');stateMachine.removeTransition({from:'active',to:'paused'});stateMachine.unsubscribe(subscriber);There are different ways you can use the state machine to manage the state of an object. Here's one example.
classDevice{constructor(){this._stateMachine=StateMachine.create('inactive');// Configure your state machine here... i.e.:this._stateMachine.addEvent('activate',[{from:'inactive',to:'active'},]);this._stateMachine.subscribe(this.handleChange.bind(this));}getState(){returnthis._stateMachine.getState();}activate(){this._stateMachine.triggerEvent('activate');}handleChange(transition){// Do more things after a successful transition}}To build distribution files, please run
To run tests, please run
To see a test coverage report, please run
To lint your code, please run
If you like to contribute, please make a pull request explaining your changes. If you want to make a suggestion or file a bug report, please create a GitHub issue.
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