Welcome to wstate 👋

A library for finite state machines.

Installation

In a browser:

<script src="state-machine.js"></script>

after downloading the source or the minified version

Using npm:

  npm install --save-dev wstate

In Node.js:

var StateMachine = require("wstate");

Usage

A state machine can be constructed using:

var fsm = new StateMachine({
  init: "solid",
  transitions: [
    { name: "melt", from: "solid", to: "liquid" },
    { name: "freeze", from: "liquid", to: "solid" },
    { name: "vaporize", from: "liquid", to: "gas" },
    { name: "condense", from: "gas", to: "liquid" },
  ],
  methods: {
    onMelt: function () {
      console.log("I melted");
    },
    onFreeze: function () {
      console.log("I froze");
    },
    onVaporize: function () {
      console.log("I vaporized");
    },
    onCondense: function () {
      console.log("I condensed");
    },
  },
});

... which creates an object with a current state property:

• fsm.state

... methods to transition to a different state:

• fsm.melt()
• fsm.freeze()
• fsm.vaporize()
• fsm.condense()

... observer methods called automatically during the lifecycle of a transition:

• onMelt()
• onFreeze()
• onVaporize()
• onCondense()

... along with the following helper methods:

• fsm.is(s) - return true if state s is the current state
• fsm.can(t) - return true if transition t can occur from the current state
• fsm.cannot(t) - return true if transition t cannot occur from the current state
• fsm.transitions() - return list of transitions that are allowed from the current state
• fsm.allTransitions() - return list of all possible transitions
• fsm.allStates() - return list of all possible states

Terminology

A state machine consists of a set of States

• solid
• liquid
• gas

A state machine changes state by using Transitions

• melt
• freeze
• vaporize
• condense

A state machine can perform actions during a transition by observing Lifecycle Events

• onBeforeMelt
• onAfterMelt
• onLeaveSolid
• onEnterLiquid
• ...

A state machine can also have arbitrary Data and Methods.

Multiple instances of a state machine can be created using a State Machine Factory.

Documentation

Read more about

• States and Transitions
• Data and Methods
• Lifecycle Events
• Asynchronous Transitions
• Initialization
• Error Handling
• State History
• Visualization
• State Machine Factory
• Upgrading from 2.x

Author

👤 keenzhang

• Github: @keenzhang

🤝 Contributing

Contributions, issues and feature requests are welcome!

Feel free to check issues page.

Show your support

Give a ⭐️ if this project helped you!

📝 License

Copyright © 2021 keenzhang.

This project is MIT licensed.