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              <div id="root">
  <!-- This div's content will be managed by React. -->
              class BuggyCounter extends React.Component {
  constructor(props) {
    this.state = { counter: 0 };
    this.handleClick = this.handleClick.bind(this);
  handleClick() {
    this.setState(({counter}) => ({
      counter: counter + 1
  render() {
    if (this.state.counter === 5) {
      // Simulate a JS error
      throw new Error('I crashed!');
    return <h1 onClick={this.handleClick}>{this.state.counter}</h1>;

function App() {
  return (
          これは React 15 系で Uncaught Error が発生したときの挙動を確認するためのサンプルです。
          <br />
          React 16 と異なり、エラー時にもコンポーネントはそのまま残り続けます。
          <br /><br />
          Click on the numbers to increase the counters.
          <br />
          The counter is programmed to throw when it reaches 5. This simulates a JavaScript error in a component.
      <hr />
      <BuggyCounter />

  <App />,

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