React中以前的状态与当前/新状态的比较

class MyComponent extends React.Component {
  state = {
    count: 0
  }

  componentDidUpdate(prevProps, prevState) {
    if (prevState.count !== this.state.count) {
      // 状态发生变化时执行特定的操作
      console.log('状态已更新');
    }
  }

  render() {
    return (
      <div>
        <button onClick={() => this.setState({ count: this.state.count + 1 })}>增加</button>
        <span>{this.state.count}</span>
      </div>
    );
  }
}

import { connect } from 'react-redux';

class MyComponent extends React.Component {
  render() {
    return (
      <div>
        <button onClick={() => this.props.increment()}>增加</button>
        <span>{this.props.count}</span>
      </div>
    );
  }
}

const mapStateToProps = (state) => {
  return {
    count: state.count
  };
};

const mapDispatchToProps = (dispatch) => {
  return {
    increment: () => dispatch({ type: 'INCREMENT' })
  };
};

export default connect(mapStateToProps, mapDispatchToProps)(MyComponent);