javascript - 将 React 计时器重置为初始 const 值

Question

当我点击重置按钮时，我试图让我的计时器应用程序重置为初始值const initState，但它只是停止计时器，而不重置值。我在 React + ES6 的 Reset initial state上尝试了许多不同的解决方案，但我得到了相同的结果：reset 按钮只是停止计时器，而没有实际重置值。到目前为止，这是我的代码：

import React, { Component } from 'react';
import moment from 'moment';
import './App.scss';
import TimerHeader from './TimerHeader';
import TimerSettings from './TimerSettings';
import TimerDisplay from './TimerDisplay';
import TimerControls from './TimerControls';
import TimerFooter from './TimerFooter';

//set initial state w/default durations, clock set to 'SESSION', and not running

const initState = {
  currentTime: moment.duration(25, 'minutes'),
  sessionTime: moment.duration(25, 'minutes'),
  breakTime: moment.duration(5, 'minutes'),
  label: 'SESSION',
  running: false,
  timer: null 
}

class App extends Component {
  constructor(props) {
    super(props)

    this.state = initState;

    this.changeSessionTime = this.changeSessionTime.bind(this);
    this.changeBreakTime = this.changeBreakTime.bind(this);
    this.switchLabel = this.switchLabel.bind(this);
    this.switchTimer = this.switchTimer.bind(this);
    this.startTimer = this.startTimer.bind(this);
    this.stopTimer = this.stopTimer.bind(this);
    this.resetTimer = this.resetTimer.bind(this);
    this.countdown = this.countdown.bind(this);
    this.playAudio = this.playAudio.bind(this);
  }

  //new function to set currentTime to either sessionTime or breakTime based on label?

  //change the session and/or break times that are displayed
  changeSessionTime(newSessionTime) {
    this.setState({
      currentTime: !this.state.running && this.state.label === 'SESSION' ? newSessionTime.clone() : this.state.currentTime,
      sessionTime: newSessionTime
    })

  }

  changeBreakTime(newBreakTime) {
    this.setState({
      currentTime: !this.state.running && this.state.label === 'BREAK' ? newBreakTime.clone() : this.state.currentTime,
      breakTime: newBreakTime
    })
  }

  //change the clock setting when an active timer hits 0
  switchLabel() {
    this.setState({
      label: this.state.label === 'SESSION' ? '\xa0' + 'BREAK' : 'SESSION'
    })
  }

  //change the timer from session to break when an active timer hits 0
  switchTimer() {
    this.setState({
      currentTime: this.state.label === 'SESSION' ? this.state.sessionTime.clone() : this.state.breakTime.clone()
    })
  }


  //start the timer when start button is clicked
  startTimer() {
    if (this.state.running) {
      return
    } else {
      this.setState({
        running: true,
        timer: setInterval(this.countdown, 1000)
      })
    }
  }

  //stop the timer when stop (i.e., pause) button is clicked
  stopTimer() {
    if (!this.state.running) {
      return
    } else {
      this.setState({
        running: false,
        timer: clearInterval(this.state.timer)
      })
    }
  }

  //reset the timer when reset button is clicked
  resetTimer() {
    clearInterval(this.state.timer)
    this.setState(initState)
  }

  //reduce timer by the second when running === true
  countdown() {
    if (this.state.running) {
      this.setState({
        currentTime: this.state.currentTime.subtract(1, 'seconds')
      })
    }

    if (this.state.running && this.state.currentTime.get('minutes') <= 0 && this.state.currentTime.get('seconds') <= 0) {
      this.playAudio();
      this.switchLabel();
      this.switchTimer();
    }

  }

  playAudio() {
    const beep = document.getElementById("beep");
    beep.play();
  }


  render() {
    return (
      <div className="container-fluid container-clock">
        <TimerHeader />
        <TimerSettings currentTime={this.state.currentTime} sessionTime={this.state.sessionTime} breakTime={this.state.breakTime} label={this.state.label} running={this.props.running} changeSessionTime={this.changeSessionTime} changeBreakTime={this.changeBreakTime} />
        <TimerDisplay currentTime={this.state.currentTime} />
        <TimerControls startTimer={this.startTimer} stopTimer={this.stopTimer} resetTimer={this.resetTimer} />
        <TimerFooter />
      </div>
    );
  }
}


export default App;

为什么不resetTimer()清除现有间隔，然后将初始值放入开头“const initState”中定义的所有值？任何见解都会有所帮助。谢谢！

标签： javascriptreactjstimerscopeconstants

Answer 1

问题是你引用同一个对象然后修改状态，基本上而不是这样做：

this.state = initState;

您需要执行以下操作：

this.state = Object.assign({}, initState);

这将解决您的问题。