An example of how simple it is to create a portal in React v16+

react16-portal.js

// @flow
/* eslint-env browser */
import * as React from 'react'
import { createPortal } from 'react-dom'

type Props = {
  children: React.Node,
}

export default class Portal extends React.Component<Props> {
  domNode: ?HTMLDivElement = null

  componentWillMount() {
    this.domNode = document.createElement('div')
    if (document.body) document.body.appendChild(this.domNode)
  }

  componentWillUnmount() {
    if (this.domNode) this.domNode.remove()
  }

  render() {
    if (this.domNode == null) return null
    return createPortal(this.props.children, this.domNode)
  }
}