clearInterval in React : <p>I'm new at React and I was trying to create a simple stopwatch with a start and stop buttons.
I'm banging my head against the wall to try to clearInterval with an onClick event on Stop button. I would declare a variable for the setInterval and then would clear it using the clearInterval. Unfortunately it is not working. 
Any tips?
Thank you in advance.</p>

<pre><code>import React, { Component } from 'react';

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

    this.startHandler = this.startHandler.bind(this);
  }

  getSeconds(time){
    return `0${time%60}`.slice(-2);
  }

  getMinutes(time){
    return Math.floor(time/60);
  }

  startHandler() {
      setInterval(()=&gt;{
      this.setState({time:this.state.time + 1});
    },1000)

  }

  stopHandler() {
    //HOW TO CLEAR INTERVAL HERE????
  }

  render () {
    return (
      &lt;div&gt;
        &lt;h1&gt;{this.getMinutes(this.state.time)}:{this.getSeconds(this.state.time)}&lt;/h1&gt;
        &lt;button onClick = {this.startHandler}&gt;START&lt;/button&gt;
        &lt;button onClick = {this.stopHandler}&gt;STOP&lt;/button&gt;
        &lt;button&gt;RESET&lt;/button&gt;
      &lt;/div&gt;
    );
  }
}

export default App;
</code></pre>
