How to use React slots

// 015 import React from 'react' using slots;
import ReactDOM from 'react-dom';
// Parent component class ParentDom extends React.Component {
    constructor(props) {
        super(props)
        this.state = {
            heardData: "header data",
            footData: "Bottom data",
            contentData: "Content data"
        }
    }
    componentDidMount() {
    }

    render() {
        return (
            <div>
                <h1>015Using slots</h1>
                <ChildDom>
                    <div data-position="heard" >This is the header</div>
                    <div data-position="content" >This is the content丨{this.state.contentData}</div>
                    <div data-position="foot" >This is the bottom</div>
                </ChildDom>
            </div>
        )
    }
}
// Child component class ChildDom extends React.Component {        
    constructor(props) {
        super(props)  
    }
    render() {
        let heard,content,foot;
        this.props.children.forEach(item =>{
            if(item.props['data-position'] == 'heard'){
                heard = item
            }else if(item.props['data-position'] == 'content'){
                content = item
            }else if(item.props['data-position'] == 'foot'){
                foot = item
            }
        })  
        return (
            <div >
                <p>I am a subcomponent</p>
               <div className="heard">
                   {heard}
               </div>
               <div className="content">
                   {content}
               </div>
               <div className="foot">
                   {foot}
               </div>
            </div>
        )
    }
}

export default function () {
    ReactDOM.render(
        <ParentDom />,
        document.querySelector("#example15")
    );
}

import React, { Component } from 'react'
import NavBar from './NavBar'
import NavBar2 from './NavBar2'

export default class App extends Component {
  render() {
    return (
      <div>
        <NavBar>
          <span>aaa</span>
          <strong>bbb</strong>
          <a href="/#" rel="external nofollow" rel="external nofollow" >ccc</a>
        </NavBar>

        <NavBar2 leftslot={<span>aaa</span>}
        centerslot={<strong>bbb</strong>}
        rightslot={<a href="/#" rel="external nofollow" rel="external nofollow" >ccc</a>}/>
      </div>
    )
  }
}

import React, { Component } from 'react'

import './style.css'
export default class NavBar extends Component {
  render () {
    return (
      <div className="nav-bar">
        <div className="nav-left">
          {this.props.children[0]}
        </div>
        <div className="nav-center">
          {this.props.children[1]}
        </div>
        <div className="nav-right">
          {this.props.children[2]}
        </div>
      </div>
    )
  }
}

import React, { Component } from 'react'

import './style.css'
export default class NavBar extends Component {
  render () {
    const {leftslot, centerslot,rightslot} = this.props
    return (
      <div className="nav-bar">
        <div className="nav-left">
          {leftslot}
        </div>
        <div className="nav-center">
          {centerslot}
        </div>
        <div className="nav-right">
          {rightslot}
        </div>
      </div>
    )
  }
}