Global keyboards events on React

Question

I'm making a small drum machine on React, and my idea is that when I press a key on the keyboard a specific sound is played depending which key was pressed. The problem I have is that I want the onKeyPress or onKeyDown event working on window scope, because if I put the event listener on an specific component that component has to be on focus to listen the event. How can I do it?

Answer 1

You can add a keydown listener on the window in the componentDidMount of your topmost component.

Example

class App extends React.Component {
  state = { lastPressedKey: null };

  componentDidMount() {
    window.addEventListener("keydown", this.handleKeyPress);
  }

  componentWillUnmount() {
    window.removeEventListener("keydown", this.handleKeyPress);
  }

  handleKeyPress = event => {
    this.setState({ lastPressedKey: event.key });
  };

  render() {
    return <div>Key last pressed: {this.state.lastPressedKey}</div>;
  }
}

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

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="root"></div>