React - Refs and ForwardRef

by Arnaud Buchholz

HTML

<div id="app"></div>

CSS

body {
  background: #20262E;
  padding: 20px;
  font-family: Helvetica;
}

#app {
  background: #fff;
  border-radius: 4px;
  padding: 20px;
  transition: all 0.2s;
}

li {
  margin: 8px 0;
}

h2 {
  font-weight: bold;
  margin-bottom: 15px;
}

.done {
  color: rgba(0, 0, 0, 0.3);
  text-decoration: line-through;
}

input {
  margin-right: 5px;
}

React

class App extends React.Component {
  constructor(props) {
    super(props);
    this.modalInputRef = React.createRef();
    // this.onClick = this.onClick.bind(this);
  }

  onClick() {
    debugger
    console.log(this.modalInputRef);
    this.modalInputRef.current.value = 'value from parent.';
  }
  
  render() {
    return (
      <div>
        <button onClick={this.onClick}>Set focus</button>
        <ModalPortal ref={this.modalInputRef} />
      </div>
    );
  }
}

class Portal extends React.Component {
  constructor(props) {
    super(props);
    this.el = document.createElement('div');
  }

  componentDidMount() {
    const root = document.querySelector('#app');
    this.el.className = 'portal-x';
    root.appendChild(this.el)
  }

  render() {
    return ReactDOM.createPortal(<input type='text' class='modal-input' ref={this.props.inputRef} />, this.el)
  }
}

const ModalPortal = React.forwardRef((props, ref) => {
  return <Portal inputRef={ref} {...props} />
});

ReactDOM.render(<App />, document.querySelector("#app"))