app-root modal component
// These two containers are siblings in the DOM
const appRoot = document.getElementById('app-root');
const modalRoot = document.getElementById('modal-root');
class Modal extends React.Component {
constructor(props) {
super(props);
this.el = document.createElement('div');
}
componentDidMount() {
// The portal element is inserted in the DOM tree after
// the Modal's children are mounted, meaning that children
// will be mounted on a detached DOM node. If a child
// component requires to be attached to the DOM tree
// immediately when mounted, for example to measure a
// DOM node, or uses 'autoFocus' in a descendant, add
// state to Modal and only render the children when Modal
// is inserted in the DOM tree.
modalRoot.appendChild(this.el);
}
componentWillUnmount() {
modalRoot.removeChild(this.el);
}
render() {
return ReactDOM.createPortal( this.props.children, this.el ); }
}
class Parent extends React.Component {
constructor(props) {
super(props);
this.state = {clicks: 0};
this.handleClick = this.handleClick.bind(this);
}
handleClick() { // This will fire when the button in Child is clicked, // updating Parent's state, even though button // is not direct descendant in the DOM. this.setState(state => ({ clicks: state.clicks + 1 })); }
render() {
return (
<div onClick={this.handleClick}> <p>Number of clicks: {this.state.clicks}</p>
<p>
Open up the browser DevTools
to observe that the button
is not a child of the div
with the onClick handler.
</p>
<Modal> <Child /> </Modal> </div>
);
}
}
function Child() {
// The click event on this button will bubble up to parent, // because there is no 'onClick' attribute defined return (
<div className="modal">
<button>Click</button> </div>
);
}
ReactDOM.render(<Parent />, appRoot);