lit-statemachine

StateMachine for Web Components, simplified integration of Xstate with LitElement. Use it as decorator if you're in a typescript evironment or use it as ES6 class mixin if you want to use in a JS environment.

Install

npm i -S @web-ui/lit-statemachine

ESM/CJS

// ES6
import { useStateMachine, useStateMachineMixin } from '@web-ui/lit-statemachine';

// CJS
const { useStateMachine, useStateMachineMixin } = require('@web-ui/lib/lit-statemachine');

Usage

live code example

As a mixin example

import { LitElement, html, css, customElement } from "lit-element";
import { useStateMachineMixin } from "@web-ui/lit-statemachine";

// Below state machine can be moved into external file
import { Machine, assign } from "xstate";
const increment = ({ count }) => count + 1;
const decrement = ({ count }) => count - 1;
const counterMachine = Machine({
  initial: "active",
  context: {
    count: 0,
  },
  states: {
    active: {
      on: {
        INC: { actions: assign({ count: increment }) },
        DEC: { actions: assign({ count: decrement }) },
      },
    },
  },
});

// UI component
export default class MyCounter extends useStateMachineMixin(LitElement, {
  machine: counterMachine,
}) {
  static get styles() {
    return css`
      span {
        width: 4rem;
        display: inline-block;
        text-align: center;
        font-size: 200%;
      }

      button {
        width: 4rem;
        height: 4rem;
        border: none;
        border-radius: 10px;
        background-color: seagreen;
        color: white;
        font-size: 200%;
      }
    `;
  }

  render() {
    const { state, send } = this.machine;

    return html`
      <button @click="${() => send("DEC")}">-</button>
      <span>${state.context.count}</span>
      <button @click="${() => send("INC")}">+</button>
    `;
  }
}

customElements.define("my-counter", MyCounter);

As a decorator example:

import { LitElement, html, css, customElement } from "lit-element";
import { useStateMachine } from '@web-ui/lit-statemachine';

// Below state machine can be moved into external file
import { Machine, assign } from "xstate";
const increment = ({ count }) => count + 1;
const decrement = ({ count }) => count - 1;

const counterMachine = Machine({
  initial: "active",
  context: {
    count: 0,
  },
  states: {
    active: {
      on: {
        INC: { actions: assign({ count: increment }) },
        DEC: { actions: assign({ count: decrement }) },
      },
    },
  },
});

// UI component
@customElement('my-counter')
@useStateMachine({ machine: counterMachine })
export default class MyCounter extends LitElement {
  render() {
    const { state, send } = this.machine;

    return html`
      <button @click="${() => send("DEC")}">-</button>
      <span>${state.context.count}</span>
      <button @click="${() => send("INC")}">+</button>
    `;
  }
}

Note: since the @customElement decorator works as static method to register element before class initiated, it has be added before the @useStateMachine()