_this8.setState不是一个函数

class MyComponent extends React.Component {
  handleClick = () => {
    this.setState({ someState: 'new value' });
  }

  render() {
    return <button onClick={this.handleClick}>Click me</button>;
  }
}

class MyComponent extends React.Component {
  constructor(props) {
    super(props);
    this.handleClick = this.handleClick.bind(this);
  }

  handleClick() {
    this.setState({ someState: 'new value' });
  }

  render() {
    return <button onClick={this.handleClick}>Click me</button>;
  }
}

class MyComponent extends React.Component {
  handleClick = () => {
    this.setState({ someState: 'new value' });
  }

  render() {
    return <button onClick={this.handleClick}>Click me</button>;
  }
}