1Portals provide a first-class way to render children into a DOM node that exists outside the DOM hierarchy of the parent component.

1ReactDOM.createPortal(child, container)
2// The first argument (child) is any renderable React child, such as an element, string, or fragment. 
3//The second argument (container) is a DOM element.

1A 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. Note: When working with portals, remember that managing keyboard focus becomes very important.