Routes.js
export default () => (
<Provider store={store}>
     <BrowserRouter>
        <Switch>
            <Route path="/posts" component={Posts} />
            <Route path="/form" component={Postform} />
            <Route exact path="/" component={App} />
            <Route path="/items" component={Items} />
            <Route path="/cart" component={Cart} />
            <Route path="/page/:id" component={Page} />
        </Switch>
    </BrowserRouter>
</Provider>
);

import React, { Component } from 'react'
import Navbar from './Navbar';
import Item from './pages/Item';

class Page extends Component {
componentDidMount(){
    const { id } = this.props.match.params;
  console.log(id);
}

render() {
return (
  <div>
    <Navbar></Navbar>
    <div>Hello</div>
  </div>
)
}
}
export default class Page;