JSPM – xstate@4.30.4

Package Exports

xstate
xstate/dist/xstate.web.js
xstate/es
xstate/es/actions
xstate/es/actions.js
xstate/es/index.js
xstate/lib
xstate/lib/Actor
xstate/lib/Actor.js
xstate/lib/State
xstate/lib/State.js
xstate/lib/actionTypes
xstate/lib/actionTypes.js
xstate/lib/actions
xstate/lib/actions.js
xstate/lib/behaviors
xstate/lib/behaviors.js
xstate/lib/devTools
xstate/lib/devTools.js
xstate/lib/index.js
xstate/lib/interpreter
xstate/lib/interpreter.js
xstate/lib/model
xstate/lib/model.js
xstate/lib/stateUtils
xstate/lib/stateUtils.js
xstate/lib/types
xstate/lib/types.js
xstate/lib/utils
xstate/lib/utils.js

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (xstate) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

_{JavaScript state machines and statecharts}

JavaScript and TypeScript finite state machines and statecharts for the modern web.

📖 Read the documentation 📑 Adheres to the SCXML specification.

Packages

🤖 xstate - Core finite state machine and statecharts library + interpreter
🔬 @xstate/fsm - Minimal finite state machine library
📉 @xstate/graph - Graph traversal utilities for XState
⚛️ @xstate/react - React hooks and utilities for using XState in React applications
✅ @xstate/test - Model-based testing utilities for XState

Super quick start

npm install xstate

import { createMachine, interpret } from 'xstate';

// Stateless machine definition
// machine.transition(...) is a pure function used by the interpreter.
const toggleMachine = createMachine({
  id: 'toggle',
  initial: 'inactive',
  states: {
    inactive: { on: { TOGGLE: 'active' } },
    active: { on: { TOGGLE: 'inactive' } }
  }
});

// Machine instance with internal state
const toggleService = interpret(toggleMachine)
  .onTransition((state) => console.log(state.value))
  .start();
// => 'inactive'

toggleService.send('TOGGLE');
// => 'active'

toggleService.send('TOGGLE');
// => 'inactive'

Visualizer
Why? (info about statecharts)
Installation
Finite State Machines
Hierarchical (Nested) State Machines
Parallel State Machines
History States

Visualizer

Visualize, simulate, and share your statecharts in XState Viz!

Why?

Statecharts are a formalism for modeling stateful, reactive systems. This is useful for declaratively describing the behavior of your application, from the individual components to the overall application logic.

Read 📽 the slides (🎥 video) or check out these resources for learning about the importance of finite state machines and statecharts in user interfaces:

Statecharts - A Visual Formalism for Complex Systems by David Harel
The World of Statecharts by Erik Mogensen
Pure UI by Guillermo Rauch
Pure UI Control by Adam Solove
Spectrum - Statecharts Community (For XState specific questions, please use the GitHub Discussions)

Finite State Machines

import { createMachine } from 'xstate';

const lightMachine = createMachine({
  id: 'light',
  initial: 'green',
  states: {
    green: {
      on: {
        TIMER: 'yellow'
      }
    },
    yellow: {
      on: {
        TIMER: 'red'
      }
    },
    red: {
      on: {
        TIMER: 'green'
      }
    }
  }
});

const currentState = 'green';

const nextState = lightMachine.transition(currentState, 'TIMER').value;

// => 'yellow'

Hierarchical (Nested) State Machines

import { createMachine } from 'xstate';

const pedestrianStates = {
  initial: 'walk',
  states: {
    walk: {
      on: {
        PED_TIMER: 'wait'
      }
    },
    wait: {
      on: {
        PED_TIMER: 'stop'
      }
    },
    stop: {}
  }
};

const lightMachine = createMachine({
  id: 'light',
  initial: 'green',
  states: {
    green: {
      on: {
        TIMER: 'yellow'
      }
    },
    yellow: {
      on: {
        TIMER: 'red'
      }
    },
    red: {
      on: {
        TIMER: 'green'
      },
      ...pedestrianStates
    }
  }
});

const currentState = 'yellow';

const nextState = lightMachine.transition(currentState, 'TIMER').value;
// => {
//   red: 'walk'
// }

lightMachine.transition('red.walk', 'PED_TIMER').value;
// => {
//   red: 'wait'
// }

Object notation for hierarchical states:

// ...
const waitState = lightMachine.transition({ red: 'walk' }, 'PED_TIMER').value;

// => { red: 'wait' }

lightMachine.transition(waitState, 'PED_TIMER').value;

// => { red: 'stop' }

lightMachine.transition({ red: 'stop' }, 'TIMER').value;

// => 'green'

Parallel State Machines

const wordMachine = createMachine({
  id: 'word',
  type: 'parallel',
  states: {
    bold: {
      initial: 'off',
      states: {
        on: {
          on: { TOGGLE_BOLD: 'off' }
        },
        off: {
          on: { TOGGLE_BOLD: 'on' }
        }
      }
    },
    underline: {
      initial: 'off',
      states: {
        on: {
          on: { TOGGLE_UNDERLINE: 'off' }
        },
        off: {
          on: { TOGGLE_UNDERLINE: 'on' }
        }
      }
    },
    italics: {
      initial: 'off',
      states: {
        on: {
          on: { TOGGLE_ITALICS: 'off' }
        },
        off: {
          on: { TOGGLE_ITALICS: 'on' }
        }
      }
    },
    list: {
      initial: 'none',
      states: {
        none: {
          on: { BULLETS: 'bullets', NUMBERS: 'numbers' }
        },
        bullets: {
          on: { NONE: 'none', NUMBERS: 'numbers' }
        },
        numbers: {
          on: { BULLETS: 'bullets', NONE: 'none' }
        }
      }
    }
  }
});

const boldState = wordMachine.transition('bold.off', 'TOGGLE_BOLD').value;

// {
//   bold: 'on',
//   italics: 'off',
//   underline: 'off',
//   list: 'none'
// }

const nextState = wordMachine.transition(
  {
    bold: 'off',
    italics: 'off',
    underline: 'on',
    list: 'bullets'
  },
  'TOGGLE_ITALICS'
).value;

// {
//   bold: 'off',
//   italics: 'on',
//   underline: 'on',
//   list: 'bullets'
// }

History States

const paymentMachine = createMachine({
  id: 'payment',
  initial: 'method',
  states: {
    method: {
      initial: 'cash',
      states: {
        cash: { on: { SWITCH_CHECK: 'check' } },
        check: { on: { SWITCH_CASH: 'cash' } },
        hist: { type: 'history' }
      },
      on: { NEXT: 'review' }
    },
    review: {
      on: { PREVIOUS: 'method.hist' }
    }
  }
});

const checkState = paymentMachine.transition('method.cash', 'SWITCH_CHECK');

// => State {
//   value: { method: 'check' },
//   history: State { ... }
// }

const reviewState = paymentMachine.transition(checkState, 'NEXT');

// => State {
//   value: 'review',
//   history: State { ... }
// }

const previousState = paymentMachine.transition(reviewState, 'PREVIOUS').value;

// => { method: 'check' }

xstate