Simple Async State Machine

Description

the objective is to provide a simple interface to build a finite state machine

Features

• thoroughly tested with good code coverage
• small package file: 3.2kb (compressed)
• written in TypeScript and therefore includes a definitions file with full documentation (*.d.ts)

Core Concepts

• Define a set of States, each with a name, a list of fromStates and some optional callbacks
• Call .transition('newStateName') to trigger a state change to the specified state
• Use Promises inside the onBeforeEnter callback to resolve/reject the state change (usually via server API)

Example Usage

import { Machine } from "ts-async-state-machine";

// Create your Machine
const MicrowaveMachine = new Machine('Microwave');

// Add States to the Machine
MicrowaveMachine.addState('off', ['running'], {
   onBeforeEnter: (prevState) => new Promise((resolve, rejection) => {
       // use a server APi request to 'confirm' the state change
       resolve();// resolves the state transition - changes 'MicrowaveMachine's state to 'off'
       // a 'rejection' will fail the internal state transition
   })
});
MicrowaveMachine.addState('on', ['off'], {
   // callbacks are optional and use them as needed: 'onEnter', 'onExit', 'onBeforeEnter' as options
   onExit: () => {
       console.log('Exited ON state')
   }
});
MicrowaveMachine.addState('running', ['on'], {
   onEnter: () => {
       console.log('Entered RUNNING State')
   }
});

// Initialise into your required starting state
MicrowaveMachine.start('off');

// Start Triggering State changes when neccessary
MicrowaveMachine.transition('on').then(newState => {
   console.log('Entered State', newState.name)
}); // omitted 'catch' for brevity

MicrowaveMachine.transition('running').then(newState => {
   console.log('Entered State', newState.name)
});

Examples

• see /examples folder for a full examples in microwave.js, traffic-light.js and traffic-light-server-stateful.js
• run microwave example: npm run example
• other examples: npm run build && node ./examples/traffic-light.js
• other examples: npm run build && node ./examples/traffic-light-server-stateful.js

Development

• build: npm run build
• test: npm run test
• code coverage: npm run test:coverage

Credits

• Inspired by the Js Async State machine lib https://github.com/robguy21/js-async-state-machine