Dziala

class Show extends React.Component {
  render() {
    return (
      <div>
        <output>{this.props.number}</output>
        <div>
        <button name="plus" onClick={this.props.handlePlus}>+</button>
        <button name="minus" onClick={this.props.handleMinus}>-</button>
        </div>
      </div>
    );
  };
}

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

  handleChange = (e) => {
    const value = parseFloat(e.target.value);
    if(Number.isNaN(value)){
      return '';
    }
    this.setState({ number: value });
  };

  handlePlus = () => {
    this.setState({ number: this.state.number + 1 })
  }
  handleMinus = () => {
    this.setState({ number: this.state.number - 1 })
  }

  render() {
    return (
      <div>
        <title>Podaj liczbe:</title>
        <input value={this.state.value} onChange={this.handleChange}></input>
        <Show
          number={this.state.number}
          handlePlus={this.handlePlus}
          handleMinus={this.handleMinus}
        />
      </div>
    );
  };
}

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