React и clearInterval

   timer() {  
        const milliseconds = this.state.milliseconds + 1000;
        const d = moment.duration(milliseconds);
        const serviceTime = Math.floor(d.asHours()) + moment.utc(milliseconds).format(":mm:ss");
        if (this.refs.timer) {
            this.setState({
                timer: serviceTime,
                milliseconds: milliseconds
            });
        }
       
    }
 
    start() {
        this.timerId = setInterval(this.timer.bind(this), 1000);
    }
 
 
    stop() {
        clearInterval(this.timerId);
    }

import React, { Component } from 'react'
import './App.css';
 
class App extends Component {
  state = {
    counter: 0
  }
 
  timer() {
    console.log('timer')
    this.setState({ counter: this.state.counter + 1 })
  }
 
  start = () => {
    console.log('start')
    this.timerId = setInterval(this.timer.bind(this), 1000);
  }
 
  stop = () => {
    console.log('stop')
    clearInterval(this.timerId);
  }
 
  render() {
    return (
      <React.Fragment>
        <div>{this.state.counter}</div>
        <div onClick={this.start.bind(this)}>старт</div>
        <div onClick={this.stop.bind(this)}>стоп</div>
      </React.Fragment>
    )
  }
}

var fake=setInterval("");
for(var i = 0 ; i < fake ; i++) {
     clearInterval(i); 
}

start = () => {
    console.log('start')
    this.timerId && clearInterval(this.timerId) // shorthand if, only else
    this.timerId = setInterval(this.timer.bind(this), 1000);
  }
 
  stop = () => {
    console.log('stop')
    clearInterval(this.timerId);
    this.timerId = null
  }

<div className='topline-right'>
    <div className='topline-right__timer'><Timer time={time}/></div>
    <div className='topline-right__number'>{num}</div>
</div>

import React, { Component } from 'react'
import './App.css';
 
class App extends Component {
  render() {
    return (
      <React.Fragment>
        <Timer />
        <Timer />
      </React.Fragment>
    )
  }
}
 
class Timer extends Component {
  state = {
    counter: 0,
    timerId: null
  }
  startStop = () => {
    console.log('click')
    if (this.state.timerId != null) {
      clearInterval(this.state.timerId)
      this.setState({ timerId: null })
    }
    else {
      this.setState({ timerId: setInterval(() => this.setState({ counter: this.state.counter + 1 }), 1000) })
    }
  }
  render() {
    return (
      <div>{this.state.counter}<button onClick={this.startStop}>{this.state.timerId == null ? 'start' : 'stop'}</button></div>
    )
  }
}
 
export default App