如何在React中添加倒计时计时器

constructor(props) {
  super(props);
  this.state = {
    countdown: 60
  };
}

render() {
  return (
    <div>
      <h1>倒计时: {this.state.countdown} 秒</h1>
    </div>
  );
}

componentDidMount() {
  this.timer = setInterval(() => {
    this.setState(prevState => ({
      countdown: prevState.countdown - 1
    }));
  }, 1000);
}

componentWillUnmount() {
  clearInterval(this.timer);
}

import React, { Component } from 'react';

class CountdownTimer extends Component {
  constructor(props) {
    super(props);
    this.state = {
      countdown: 60
    };
  }

  componentDidMount() {
    this.timer = setInterval(() => {
      this.setState(prevState => ({
        countdown: prevState.countdown - 1
      }));
    }, 1000);
  }

  componentWillUnmount() {
    clearInterval(this.timer);
  }

  render() {
    return (
      <div>
        <h1>倒计时: {this.state.countdown} 秒</h1>
      </div>
    );
  }
}

export default CountdownTimer;

import React from 'react';
import CountdownTimer from './CountdownTimer';

function App() {
  return (
    <div>
      <CountdownTimer />
    </div>
  );
}

export default App;