React Bootstrap4 modal placement

Question

I've got a component that opens a bootstrap modal (using react-bootstrap4-modal)

It opens and closes using this

{this.state.inEditMode ? <MemberModal /> : null}

However, because the component is already nested somewhere in the DOM, it's not a valid placement for bootstrap modal markup. It leaves a nasty white bar at the bottom, which I confirmed does not happen if it's located within the outermost <App/> div tag.

Is there a simple way to fix this? Or will it require me putting all of my modal components within <App/> and changing the state of <App/> from within nested children?

Answer 1

This is a z-index stacking issue and was a common problem until React introduced portals. Dan Abrimov from the FB team put together a code pen with an example that can be found here.

Portals provide a first-class way to render children into a DOM node that exists outside the DOM hierarchy of the parent component.

A typical use case for portals is when a parent component has an overflow: hidden or z-index style, but you need the child to visually “break out” of its container. For example, dialogs, hovercards, and tooltips.

Normally, when you return an element from a component’s render method, it’s mounted into the DOM as a child of the nearest parent node:

render() {
  // React mounts a new div and renders the children into it
  return (
    <div>
      {this.props.children}
    </div>
  );
}

However, sometimes it’s useful to insert a child into a different location in the DOM:

render() {
  // React does *not* create a new div. It renders the children into `domNode`.
  // `domNode` is any valid DOM node, regardless of its location in the DOM.
  return ReactDOM.createPortal(
    this.props.children,
    domNode
  );
}