@ggoodman/fsm
Fully typed finite state machine for JavaScript and TypeScript
Installation
npm install @ggoodman/fsmExample
The example below demonstrates a traffic light that cycles eternally on a timer.
Note: Instead of defining the 'tick' event, we could have called
ctx.transitionTo('red' | 'green' | 'yellow')directly.
import { DefineEvent, DefineState, Service } from '@ggoodman/fsm';
type Red = DefineState<'red'>;
type Yellow = DefineState<'yellow'>;
type Green = DefineState<'green'>;
type Tick = DefineEvent<'tick'>;
const service = Service.define<Red | Yellow | Green, Tick>(
(s) =>
s
.defineState('red', (red) =>
red
.onEnter((ctx) => ctx.runAfter(30 * 1000, (ctx) => ctx.send('tick')))
.onEvent('tick', (ctx) => ctx.transitionTo('green'))
)
.defineState('green', (red) =>
red
.onEnter((ctx) => ctx.runAfter(60 * 1000, (ctx) => ctx.send('tick')))
.onEvent('tick', (ctx) => ctx.transitionTo('yellow'))
)
.defineState('yellow', (red) =>
red
.onEnter((ctx) => ctx.runAfter(10 * 1000, (ctx) => ctx.send('tick')))
.onEvent('tick', (ctx) => ctx.transitionTo('red'))
),
'red'
);
service.onStateChange((state) => {
console.log('State changed to %s', state.id);
});
service.start();
// State changed to red
// State changed to green
// State changed to yellow
// ...