React.jsでカレンダーを作ろう 2

さて、React.js + webpack + babelの環境ができたので、カレンダーを作っていきます。

# react-calendar のインストール
$ npm install react-calendar

jsはこうかな。

import React, { Component } from "react";
import ReactDOM from "react-dom";
import Calendar from 'react-calendar';

class Layout extends Component {
	state = {
		date: new Date(),
	}

	onChange = date => this.setState({ date })

	render(){
		return (
			<div>
				<Calendar
					onChange={this.onChange}
					value={this.state.date}
				/>
			</div>
		);
	}
}

const app = document.getElementById('app');
ReactDOM.render(<Layout/>, app);

$ npm start

ERROR in ./js/client.js
Module build failed (from ../node_modules/babel-loader/lib/index.js):
SyntaxError: /home/vagrant/react/src/js/client.js: Support for the experimental syntax ‘classProperties’ isn’t currently enabled (6:8):

4 |
5 | class Layout extends React.Component {
> 6 | state = {
| ^
7 | date: new Date(),
8 | }
9 |
Add @babel/plugin-proposal-class-properties (https://git.io/vb4SL) to the ‘plugins’ section of your Babel config to enable transformation

ん？　これが必要？