Sample code for react-infinite using ES6 syntax without React.createClass

I want to implement infinite scroll in my app.
I found https://github.com/bvaughn/react-virtualized, but it's a bit heavy. I want to use a simple and thin one, and then I found react-infinite

react-infinite
https://github.com/seatgeek/react-infinite

sample code for react-infinite with a create-react-app environment

• using create-react-app
• using ES6 syntax
• without React.createClass

NOTE

• this sample code has elements in React Component's state
  It's a bit weird.

code

import React, { Component } from 'react';
import Infinite from 'react-infinite';
import logo from './logo.svg';
import './App.css';

class App extends Component {
  render() {
    return (
      <div className="App">
        <div className="App-header">
          <img src={logo} className="App-logo" alt="logo" />
          <h2>Welcome to React</h2>
        </div>
        <p className="App-intro">
          To get started, edit <code>src/App.js</code> and save to reload.
        </p>
        <InfiniteList />
      </div>
    );
  }
}

class ListItem extends React.Component {

  render () {
    return (
      <div className="infinite-list-item">
        List Item {this.props.num}
      </div>
    );
  };
};


class InfiniteList extends React.Component {
  constructor (props) {
    super(props);
    this.state = {
      elements: this.buildElements(0, 100),
      isInfiniteLoading: false
    };
  }

  buildElements (start, end) {
    let elements = [];
    for (let i = start; i < end; i++) {
      elements.push(<ListItem key={i}/>)
    }
    return elements;
  }

  handleInfiniteLoad () {
    let that = this;
    this.setState({
      isInfiniteLoading: true
    });
    setTimeout(function() {
      let elemLength = that.state.elements.length,
        newElements = that.buildElements(elemLength, elemLength + 1000);
      that.setState({
        isInfiniteLoading: false,
        elements: that.state.elements.concat(newElements)
      });
    }, 2500);
  }

  elementInfiniteLoad () {
    return <div className="infinite-list-item">
      Loading...
    </div>;    
  }

  render () {
    return <Infinite elementHeight={40}
      containerHeight={250}
      infiniteLoadingBeginBottomOffset={200}
      onInfiniteLoad={this.handleInfiniteLoad}
      loadingSpinnerDelegate={this.elementInfiniteLoad()}
      isInfiniteLoading={this.state.isInfiniteLoading}
    >
      {this.state.elements}
    </Infinite>;
  }
};


export default App;

Gif