This tutorial introduces React Router 4, the last stable version

React Router is the de-facto React routing library, and it’s one of the most popular projects built on top of React.

React at its core is a very simple library, and it does not dictate anything about routing.

Routing in a Single Page Application is the way to introduce some features to navigating the app through links, which are expected in normal web applications:

  1. The browser should change the URL when you navigate to a different screen
  2. Deep linking should work: if you point the browser to a URL, the application should reconstruct the same view that was presented when the URL was generated.
  3. The browser back (and forward) button should work like expected.

Routing links together your application navigation with the navigation features offered by the browser: the address bar and the navigation buttons.

React Router offers a way to write your code so that it will show certain components of your app only if the route matches what you define.

Installation

With npm:

npm install react-router-dom

Types of routes

React Router provides two different kind of routes:

  • BrowserRouter
  • HashRouter

One builds classic URLs, the other builds URLs with the hash:

https://application.com/dashboard   /* BrowserRouter */
https://application.com/#/dashboard /* HashRouter    */

Which one to use is mainly dictated by the browsers you need to support. BrowserRouter uses the History API, which is relatively recent, and not supported in IE9 and below. If you don’t have to worry about older browsers, it’s the recommended choice.

Components

The 3 components you will interact the most when working with React Router are:

  • BrowserRouter, usually aliased as Router
  • Link
  • Route

BrowserRouter wraps all your Route components.

Link components are - as you can imagine - used to generate links to your routes

Route components are responsible for showing - or hiding - the components they contain.

BrowserRouter

Here’s a simple example of the BrowserRouter component. You import it from react-router-dom, and you use it to wrap all your app:

import React from 'react'
import ReactDOM from 'react-dom'
import { BrowserRouter as Router } from 'react-router-dom'

ReactDOM.render(
  <Router>
      <div>
        <!-- -->
      </div>
  </Router>,
  document.getElementById('app')
)

A BrowserRouter component can only have one child element, so we wrap all we’re going to add in a div element.

The Link component is used to trigger new routes. You import it from react-router-dom, and you can add the Link components to point at different routes, with the to attribute:

import React from 'react'
import ReactDOM from 'react-dom'
import { BrowserRouter as Router, Link } from 'react-router-dom'

ReactDOM.render(
  <Router>
      <div>
        <aside>
          <Link to={`/dashboard`}>Dashboard</Link>
          <Link to={`/about`}>About</Link>
        </aside>
        <!-- -->
      </div>
  </Router>,
  document.getElementById('app')
)

Route

Now let’s add the Route component in the above snippet to make things actually work as we want:

import React from 'react'
import ReactDOM from 'react-dom'
import { BrowserRouter as Router, Link, Route } from 'react-router-dom'

const Dashboard = () => (
  <div>
    <h2>Dashboard</h2>
    ...
  </div>
)

const About = () => (
  <div>
    <h2>About</h2>
    ...
  </div>
)

ReactDOM.render(
  <Router>
    <div>
      <aside>
        <Link to={`/`}>Dashboard</Link>
        <Link to={`/about`}>About</Link>
      </aside>

      <main>
        <Route exact path='/' component={Dashboard} />
        <Route path='/about' component={About} />
      </main>
    </div>
  </Router>,
  document.getElementById('app')
)

Check this example on Glitch: https://glitch.com/edit/#!/flaviocopes-react-router-v4/

When the route matches /, the application shows the Dashboard component.

When the route is changed by clicking the “About” link to /about, the Dashboard component is removed and the About component is inserted in the DOM.

Notice the exact attribute. Without this, path="/" would also match /about, since / is contained in the route.

Match multiple paths

You can have a route respond to multiple paths using a regex, because path can be a regular expressions string:

<Route path='/(about|who)/' component={Dashboard} />

Inline rendering

Instead of specifying a component property on Route, you can set a render prop:

<Route
  path='/(about|who)/'
  render={() => (
    <div>
      <h2>About</h2>
      ...
    </div>
  )}
/>

Match dynamic route parameter

You already saw how to use static routes like

const Posts = () => (
  <div>
    <h2>Posts</h2>
    ...
  </div>
)

//...

<Route exact path="/posts" component={Posts} />

Here’s how to handle dynamic routes:

const Post = ({match}) => (
  <div>
    <h2>Post #{match.params.id}</h2>
    ...
  </div>
)

//...

<Route exact path="/post/:id" component={Post} />

In your Route component you can lookup the dynamic parameters in match.params.

match is also available in inline rendered routes, and this is especially useful in this case, because we can use the id parameter to lookup the post data in our data source before rendering Post:

const posts = [
  { id: 1, title: 'First', content: 'Hello world!' },
  { id: 2, title: 'Second', content: 'Hello again!' }
]

const Post = ({post}) => (
  <div>
    <h2>{post.title}</h2>
    {post.content}
  </div>
)

//...

<Route exact path="/post/:id" render={({match}) => (
  <Post post={posts.find(p => p.id === match.params.id)} />
)} />

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