每秒更新一次 React 组件

javascript reactjs

2022-08-30 01:57:46

我一直在玩 React，并有以下时间组件，它只是渲染到屏幕上：Date.now()

import React, { Component } from 'react';

class TimeComponent extends Component {
  constructor(props){
    super(props);
    this.state = { time: Date.now() };
  }
  render(){
    return(
      <div> { this.state.time } </div>
    );
  }
  componentDidMount() {
    console.log("TimeComponent Mounted...")
  }
}

export default TimeComponent;

让这个组件每秒更新一次以从 React 的角度重新绘制时间的最佳方法是什么？

答案 1

您需要使用来触发更改，但还需要在组件卸载时清除计时器，以防止它留下错误并泄漏内存：setInterval

componentDidMount() {
  this.interval = setInterval(() => this.setState({ time: Date.now() }), 1000);
}
componentWillUnmount() {
  clearInterval(this.interval);
}

答案 2

下面的代码是 React.js 网站的修改示例。

原始代码可在此处找到：https://reactjs.org/#a-simple-component

class Timer extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      seconds: parseInt(props.startTimeInSeconds, 10) || 0
    };
  }

  tick() {
    this.setState(state => ({
      seconds: state.seconds + 1
    }));
  }

  componentDidMount() {
    this.interval = setInterval(() => this.tick(), 1000);
  }

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

  formatTime(secs) {
    let hours   = Math.floor(secs / 3600);
    let minutes = Math.floor(secs / 60) % 60;
    let seconds = secs % 60;
    return [hours, minutes, seconds]
        .map(v => ('' + v).padStart(2, '0'))
        .filter((v,i) => v !== '00' || i > 0)
        .join(':');
  }

  render() {
    return (
      <div>
        Timer: {this.formatTime(this.state.seconds)}
      </div>
    );
  }
}

ReactDOM.render(
  <Timer startTimeInSeconds="300" />,
  document.getElementById('timer-example')
);