App.js

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

import React, { Component, createElement } from 'react';
import PropTypes from 'prop-types';

class BuiltEmitter extends Component {
  static propTypes = {
    feature: PropTypes.func.isRequired,
  };

  componentDidMount() {
    const { feature } = this.props;

    // Class components must call this.props.onReady when they're ready for the test.
    // We will assume functional components are ready immediately after mounting.
    if (!Component.isPrototypeOf(feature)) {
      this.handleReady();
    }
  }

  handleReady() {
    document.dispatchEvent(new Event('ReactFeatureDidMount'));
  }

  render() {
    const { props: { feature }, handleReady } = this;
    return (
      <div>
        {createElement(feature, {
          onReady: handleReady,
        })}
      </div>
    );
  }
}

class App extends Component {
  constructor(props) {
    super(props);

    this.state = { feature: null };

    this.setFeature = this.setFeature.bind(this);
  }

  componentDidMount() {
    const feature = window.location.hash.slice(1);
    switch (feature) {
      case 'array-destructuring':
        import('./features/syntax/ArrayDestructuring').then(f =>
          this.setFeature(f.default)
        );
        break;
      case 'array-spread':
        import('./features/syntax/ArraySpread').then(f =>
          this.setFeature(f.default)
        );
        break;
      case 'async-await':
        import('./features/syntax/AsyncAwait').then(f =>
          this.setFeature(f.default)
        );
        break;
      case 'class-properties':
        import('./features/syntax/ClassProperties').then(f =>