withPortal.js

import React, { Component } from 'react';
import ReactDOM from 'react-dom';

export default Comp => (
  class HOC extends Component {
    constructor(props) {
      super(props);
      this.el = document.createElement('div');
    }
    componentDidMount() {
      document.body.appendChild(this.el);
    }
    componentWillUnmount() {
      this.el.parentNode.removeChild(this.el);
    }
    render() {
      return ReactDOM.createPortal(<Comp {...this.props} />, this.el);
    }
  }
);