zadanie00.jsx

import React from 'react';
import ReactDOM from 'react-dom';

document.addEventListener('DOMContentLoaded', function(){
    class Nonsense extends React.Component {
        constructor(props){
            super(props);

            this.state = {
                buttonsText  : 'Klik!',
                thirdBtnWidth: 'auto',
            };
        }
        handleFirstBtnClick = () => {
            console.log( 'Pierwszy przycisk kliknięty' );
        };
        handleSecondBtnClick = () => {
            this.setState({
                buttonsText : 'Click!',
            });
        };
        handleThirdBtnClick = () => {
            this.setState({
                thirdBtnWidth : '300px',
            });
        };
        render(){
            return <div>
                <button onClick={this.handleFirstBtnClick}>
                    {this.state.buttonsText}
                </button>
                <button onClick={this.handleSecondBtnClick}>
                    {this.state.buttonsText}
                </button>
                <button onClick={this.handleThirdBtnClick} style={{width:this.state.thirdBtnWidth}}>
                    {this.state.buttonsText}
                </button>
            </div>;
        }
    }

    class App extends React.Component {
        render(){
            return <Nonsense />;
        }
    }

    ReactDOM.render(
        <App />,
        document.getElementById('app')
    );
});