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Version: XState v5

XState

XState is a state management and orchestration solution for JavaScript and TypeScript apps.

It uses event-driven programming, state machines, statecharts, and the actor model to handle complex logic in predictable, robust, and visual ways. XState provides a powerful and flexible way to manage application and workflow state by allowing developers to model logic as actors and state machines. It integrates well with React, Vue, Svelte, and other frameworks and can be used in the frontend, backend, or wherever JavaScript runs.

Installation​

XState is available on npm:

yarn add xstate

Create a simple machine​

import { createMachine, interpret } from 'xstate';

const countMachine = createMachine({
  context: {
    count: 0,
  },
  on: {
    INC: {
      actions: assign({
        count: ({ context }) => context.count + 1,
      }),
    },
    DEC: {
      actions: assign({
        count: ({ context }) => context.count - 1,
      }),
    },
    SET: {
      actions: assign({
        count: ({ event }) => event.value,
      }),
    },
  },
});

const countActor = interpret(countMachine).start();

countActor.subscribe((state) => {
  console.log(state.context.count);
});

countActor.send({ type: 'INC' });
// logs 1
countActor.send({ type: 'DEC' });
// logs 0
countActor.send({ type: 'SET', value: 10 });
// logs 10

Create a more complex machine​

import { createMachine, interpret } from 'xstate';

const textMachine = createMachine({
  context: {
    committedValue: '',
    value: '',
  },
  initial: 'reading',
  states: {
    reading: {
      on: {
        'text.edit': { target: 'editing' },
      },
    },
    editing: {
      on: {
        'text.change': {
          actions: assign({
            value: ({ event }) => event.value,
          }),
        },
        'text.commit': {
          actions: assign({
            committedValue: ({ context }) => context.value,
          }),
          target: 'reading',
        },
        'text.cancel': {
          actions: assign({
            value: ({ context }) => context.committedValue,
          }),
          target: 'reading',
        },
      },
    },
  },
});

const textActor = interpret(textMachine).start();

textActor.subscribe((state) => {
  console.log(state.context.value);
});

textActor.send({ type: 'text.edit' });
// logs ''
textActor.send({ type: 'text.change', value: 'Hello' });
// logs 'Hello'
textActor.send({ type: 'text.commit' });
// logs 'Hello'
textActor.send({ type: 'text.edit' });
// logs 'Hello'
textActor.send({ type: 'text.change', value: 'Hello world' });
// logs 'Hello world'
textActor.send({ type: 'text.cancel' });
// logs 'Hello'

Download the XState VS Code extension​

Read more about our developer tools.

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/vue: Vue composition functions and utilities for using XState in Vue applications
  • 🎷 @xstate/svelte: Svelte utilities for using XState in Svelte applications
  • ✅ @xstate/test: Model-Based-Testing utilities (using XState) for testing any software
  • 🔍 @xstate/inspect: Inspection utilities for XState