storybook/examples/official-storybook/config.js

import React from 'react';
import { ThemeProvider } from 'emotion-theming';
import { configure, addDecorator } from '@storybook/react';
import { themes } from '@storybook/components';
import { setOptions } from '@storybook/addon-options';
import { configureViewport, INITIAL_VIEWPORTS } from '@storybook/addon-viewport';

import 'react-chromatic/storybook-addon';
import addHeadWarning from './head-warning';
import extraViewports from './extra-viewports.json';

addHeadWarning('Preview head not loaded', 'preview-head-not-loaded');
addHeadWarning('Dotenv file not loaded', 'dotenv-file-not-loaded');

setOptions({
  hierarchySeparator: /\/|\./,
  hierarchyRootSeparator: /\|/,
  theme: themes.dark,
});

addDecorator(story => <ThemeProvider theme={themes.normal}>{story()}</ThemeProvider>);

configureViewport({
  viewports: {
    ...INITIAL_VIEWPORTS,
    ...extraViewports,
  },
});

function importAll(req) {
  req.keys().forEach(filename => req(filename));
}

function loadStories() {
  let req;
  req = require.context('../../lib/ui/src', true, /\.stories\.js$/);
  importAll(req);

  req = require.context('../../lib/components/src', true, /\.stories\.js$/);
  importAll(req);

  req = require.context('./stories', true, /\.stories\.js$/);
  importAll(req);
}

configure(loadStories, module);