Storybook is an open source tool for developing UI components in isolation for React, Vue, Angular, and more. It makes building stunning UIs organized and efficient.


At first we must install storybook to our Merkur project. The best way is using the Storybook CLI to install it in a single command.

npx storybook@latest init

After that we install merkur module for easy integration.

npm i @merkur/tool-storybook --save-dev

Now we must update storybook file ./storybook/preview.js similarly to the example below.

// ./storybook/preview.js
import { createPreactWidget } from '@merkur/preact/client';

// helper method for creating storybook loader, which async creates our widget instance.
import { createWidgetLoader } from '@merkur/tool-storybook';

// Imports for updating storybook playground.
import { FORCE_RE_RENDER } from '@storybook/core-events';
import { addons } from '@storybook/preview-api';

import WidgetContext from '../src/components/WidgetContext';
// receive widget properties for creating our Merkur widget instance
import widgetProperties from '../src/widget';

// register our widget to Merkur

// defined our custom widget loader
export const loaders = [
    render: () => {
      addons.getChannel().emit(FORCE_RE_RENDER); // widget must be able to update the storybook playground
    widgetProperties, // created widget properties

// if you need Context in React or Preact widget you must define Context Provider.
export const decorators = [
   (Story, { loaded: { widget }}) => {
    return (
      <WidgetContext.Provider value={widget}>
        <Story />

Note: If you use any pre-processors (webpack loaders) for building CSS styles you should also define then in webpackFinal function by extending given config object. More on that topic can be found in official Storybook documentation.

That’s all. Now we can write our stories.

How to write stories

You can use every format which Storybook offers. For example we pick up named exports format and our counter component from demo page for Preact preview.

// /src/component/Counter.jsx
import { useContext } from 'preact/hooks';
import WidgetContext from './WidgetContext';

export default function Counter({ counter }) {
  const widget = useContext(WidgetContext);

  return (
      <h3>Counter widget:</h3>
      <p>Count: {counter}</p>
      <button onClick={widget.onClick}>increase counter</button>
      <button onClick={widget.onReset}>reset counter</button>

// /src/component/Counter.stories.jsx
import Counter from './Counter';

export default {
  title: 'Counter',
  args: {
    // Every Merkur story must have defined props property
    widget: {
      props: {},

const Template = (args, { loaded: { widget } }) => {
  return <Counter counter={widget.state.counter} />

export const DefaultCounter = Template.bind({});

export const TenCounter = Template.bind({});
TenCounter.args = {
  widget: {
    props: {},
    // change default widget state from 0 to 10
    state: {
      counter: 10,

Now run command npm run storybook and you will see our Counter component with two settings.