setState不会在react中第一次更新

this.setState({ key: value }, () => {
  // 这里的代码会在状态更新后执行
});

componentDidUpdate(prevProps, prevState) {
  if (prevState.key !== this.state.key) {
    // 状态已更新，可以在这里执行相关操作
  }
}

import React, { Component } from 'react';

class Counter extends Component {
  constructor(props) {
    super(props);
    this.state = { count: 0 };
  }

  increment = () => {
    this.setState(
      (prevState) => ({ count: prevState.count + 1 }),
      () => {
        console.log('New count:', this.state.count);
      }
    );
  };

  render() {
    return (
      <div>
        <p>Count: {this.state.count}</p>
        <button onClick={this.increment}>Increment</button>
      </div>
    );
  }
}

export default Counter;