Package Exports

@xstate/fsm

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Readme

@xstate/fsm

This package contains a minimal implementation of XState for finite state machines.

Features:

Finite states (non-nested)
Initial state
Transitions (object or strings)
Context
Entry actions
Exit actions
Transition actions
state.changed

If you want to use statechart features such as nested states, parallel states, history states, activities, invoked services, delayed transitions, transient transitions, etc. please use XState.

Usage

import { FSM, assign } from '@xstate/fsm';

const lightFSM = FSM({
  id: 'light',
  initial: 'green',
  context: { redLights: 0 },
  states: {
    green: {
      on: {
        TIMER: 'yellow'
      }
    },
    yellow: {
      on: {
        TIMER: {
          target: 'red',
          actions: () => console.log('Going to red!')
        }
      }
    },
    red: {
      entry: assign({ redLights: ctx => ctx.redLights + 1 }),
      on: {
        TIMER: 'green'
      }
    }
  }
});

const { initialState } = lightFSM;
// {
//   value: 'green',
//   context: { redLights: 0 },
//   actions: [],
//   changed: undefined
// }

const yellowState = lightFSM.transition(initialState, 'TIMER');
// {
//   value: 'yellow',
//   context: { redLights: 0 },
//   actions: [
//     { type: undefined, exec: () => console.log('Going to red!') }
//   ],
//   changed: true
// }

const redState = lightFSM.transition(yellowState, 'TIMER');
// {
//   value: 'red',
//   context: { redLights: 1 },
//   actions: [],
//   changed: true
// }