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.

Because Storybook hasn’t official support for Webpack@5. We must install html-webpack-plugin@next.

npm i --save-dev html-webpack-plugin@next

After that we install merkur module for easy integration.

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

Now we must update two storybook files ./storybook/preview.js and ./storybook/main.js. At first we update our ./storybook/preview.js similarly to the example below.

// ./storybook/preview.js
// register our widget to Merkur
import '../src/client';

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

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

// Specific imports for your chosen view. For example Preact:
import { h } from 'preact';
import { forceReRender } from '@storybook/preact';
import WidgetContext from '../src/component/WidgetContext';

// defined our custom widget loader
export const loaders = [
    render: forceReRender, // 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 />

Then, we add to storybook’s webpack config handling of *.mjs files. Fortunately, it’s easy.

// ./storybook/main.js
module.exports = {
  webpackFinal: async (config) => {
      test: /\.mjs$/,
      include: /node_modules/,
      type: "javascript/auto"

    return config;

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 { h } from 'preact'; // eslint-disable-line no-unused-vars
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
/** @jsx h */
import { h } from 'preact';
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.