JavaScript State Machine is a lightweight library for creating finite state machines in JavaScript. It provides a simple and intuitive API for defining states, transitions, and callbacks, making it easy to model complex behaviors and manage application state.

Pros

• Easy to use and understand, with a clean and straightforward API
• Lightweight and dependency-free, suitable for both browser and Node.js environments
• Supports asynchronous transitions and lifecycle events
• Extensible through plugins and custom visualization options

Cons

• Limited built-in visualization options compared to some other state machine libraries
• May require additional effort to integrate with complex application architectures
• Documentation could be more comprehensive, especially for advanced use cases
• Not actively maintained, with the last major update in 2018

Code Examples

1. Creating a simple state machine:

const 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') }
  }
});

2. Transitioning between states:

fsm.melt();  // logs: 'I melted'
console.log(fsm.state);  // 'liquid'
fsm.vaporize();
console.log(fsm.state);  // 'gas'

3. Using asynchronous transitions:

const fsm = new StateMachine({
  init: 'pending',
  transitions: [
    { name: 'resolve', from: 'pending', to: 'resolved' },
    { name: 'reject', from: 'pending', to: 'rejected' }
  ],
  methods: {
    onResolve: function() {
      return new Promise((resolve) => {
        setTimeout(() => {
          console.log('Resolved after 1 second');
          resolve();
        }, 1000);
      });
    }
  }
});

await fsm.resolve();  // logs: 'Resolved after 1 second'

Getting Started

1. Install the library:

   npm install javascript-state-machine
   

2. Import and use in your project:

   import StateMachine from 'javascript-state-machine';
   
   const fsm = new StateMachine({
     init: 'idle',
     transitions: [
       { name: 'start', from: 'idle', to: 'running' },
       { name: 'pause', from: 'running', to: 'paused' },
       { name: 'resume', from: 'paused', to: 'running' },
       { name: 'stop', from: ['running', 'paused'], to: 'idle' }
     ],
     methods: {
       onStart: function() { console.log('Started') },
       onStop: function() { console.log('Stopped') }
     }
   });
   
   fsm.start();  // logs: 'Started'
   console.log(fsm.state);  // 'running'