React - router

router.js

import React from 'react';
import { BrowserRouter as Router, Link, Route } from 'react-router-dom';
import Footer from './Footer';
import Header from './Header';
import Todos from './Todos';
import Articles from './Articles';

export default class Layout extends React.Component {
  constructor() {
    super();
    this.state = {
      header: "My first React app",
      footer: "by Dariusz Glowinski"
    }
  }
  render() {
    const marginStyle = {
      marginTop: "60px"
    }
    return (
      <Router>
        <div  >
          <Header header={this.state.header} />  
            <Link to="/todos" > Todos </Link> <Link to="/articles"><button>Articles</button></Link>
            <hr style={marginStyle}/>
            <Route exact={true} path="/"  render={()=>(
              <h1> Welcome </h1>
            )}/>
            <Route path="/todos" component={Todos}/>
            <Route path="/articles" component={Articles}/>
            <hr style={marginStyle}/>
          <Footer footer={this.state.footer} />
        </div>
      </Router>
    );
  }
}