未定义React.js this.props，除非刷新页面

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

  handleClick() {
    console.log(this.props); // 现在可以正确访问 this.props
  }

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

class MyComponent extends React.Component {
  handleClick = () => {
    console.log(this.props); // 箭头函数自动绑定 this
  }

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

class MyComponent extends React.Component {
  componentDidMount() {
    console.log(this.props); // 在 componentDidMount 中访问 this.props 是安全的
  }

  render() {
    return <div>{this.props.message}</div>;
  }
}

import React from 'react';

class ParentComponent extends React.Component {
  render() {
    return <ChildComponent message="Hello, World!" />;
  }
}

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

  handleClick() {
    console.log(this.props.message); // 输出: Hello, World!
  }

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

export default ParentComponent;