app.js

import React, { Component } from 'react';
import Progress from 'components/Progress';
import ProgressInput from 'components/ProgressInput';

class App extends Component {
  state = {
    count: 10
  }

  onChangeCount = count => {
    this.setState({count});
  }

  render() {
    return <div>
      <div>
        O progresso é {this.state.count}
      </div>

      <Progress value={this.state.count} />
      <ProgressInput value={this.state.count} onChange={this.onChangeCount}/>

      <div>
        <button onClick={(evt) => this.onChangeCount(this.state.count + 1) }>Increment</button>
        <button onClick={(evt) => this.onChangeCount(this.state.count - 1) }>Decrement</button>
      </div>
    </div>
  }
}

export default App;