React Router

August 13, 2019

This has been the toughest week at Lambda School for me so far. What was so hard about it? Learning React router.

I managed to finish the projects and get the apps working, but didn't fully understand why or how everything worked. This post is a recap of my notes to solidify my knowledge.

Routing: the process of determining what code to run when a URL is requested

A server-side route is when a user clicks on a link and new page is requested from the server. It completely discards the old page before serving the new document to the user.

Pros of server-side routing:

  • A server-side route will only request the page that's needed
  • Better for SEO (currently)

Cons of server-side routing:

  • Every request results in a full-page refresh, which means unnecessary data is being requested (eg. header/footer)
  • It can take a while for the page to be rendered (if the document is large or internet is slow)

A client-side route happens when the route is handled internally by the JavaScript that is loaded on the page. When a user clicks on a link, the URL changes but the request to the server is prevented. The whole page won't refresh - there are just some elements inside the application that will change.

Pros of client-side routing:- Routing between views is generally faster because less data is processed - Smooth transitions and animations between views is easier to implementCons of client-side routing:- The whole website or application needs to be loaded on the first request (and the user may not need all the data) - It requires more setup work or even a library - Less optimized for SEO

React Router is declarative style routing for React applications.

The Route component is how we declare what components will be mounted based on what URLs are requested by the user. It takes in a few props:

  • path: the React component will trigger when the URL matches this path
  • component: the component you want React to mount when the URL matches the requested path


<Route path="/" component={Home}/>
<Route path="/contact" component={Contact}/>
<Route path="/about" component={About}/>

exact - by placing exact on a <Route /> component, we are saying that the specific component will be requested only if the path matches exactly what was requested

Eg. <Route exact path="/" component={Home}/>

The Link component:

To get our app to work with client-side routing, we use the <Link> component instead of anchor tags (<a>).

EG. <Link to="/about">About</Link> will link to the About component (Assuming that <Route path="/about" component={About} /> was set up)

On dynamic routing:

Essentially, dynamic routing is routing that takes place as our app is rendering. Any component that is mounted via the <Route> component will receive match, history, and location objects as props. Lets focus on the match object for now. Say we have a route that looks like:

<Route path='/books/:bookId' component={Book} />

:bookId in the URL is essentially a variable for the actually path that the user navigates too. We can access the value of :bookId inside the <Book> component by referencing props.match.params.bookId. For example, if the user navigates to "/books/10", props.match.params.bookId inside <Book> would equal 10. And the <Book> component displays different data as the :bookId changes.

On passing down props via <Route>:

What if we wanted to pass down data to the component specified in <Route>?

We can use render props. render is a prop on the <Route> component that takes in a function that returns the component that we want to render. We can pass down data via render props like so :

<Route render={(props) => (

Using the ES6 spread operator, it would look like:

<Route render={(props) => (

On nested routes:

Say we have a <Product> component that renders when a user goes to /products/:productId, and there's a section that has tabs for Details and Shipping. We want to mount and render nested components under the tabs (when they're clicked) while updating the URL based on the active tab. (I.e. /products/:productId/details, products/:productId/shipping). However, when switching between tabs, we don't want to re-render the whole <Product> component.

<Route /> is just a component. So if we want to nest a set of routes inside another route, we can just render those child Route components inside a parent Route component!

On the history prop:
In some cases, we want to load different routes or components in response to events other than a user clicking on a <Link/>. We can use the <Route> component's history prop to do this.

Remember when I noted: Any component that is mounted via the <Route> component will receive match, history, and location objects as props.

By putting props.history.push(<new URL path>) inside an event handler function, our app will navigate to that path when the event is triggered. For example:

function Home(props) {
  return (
      <button onClick={todaySpecials}>Today's Specials!</button>

  function todaySpecials() {

On <Link> vs <NavLink>:

The <Link> component renders an anchor tag with an href of the path we have specified on it.
The <NavLink> component is almost identical to the <Link> component there's just one difference. It adds the class active to the anchor tag when the URL matches the path in the <NavLink> component. With this feature, we can now style our navigation based on which route we are on!

Also, if we want the class to be a different name, we can use the activeClassName prop on the <NavLink> component to set it to something else. For example:

<NavLink to="/" activeClassName="activeNavButton">Home</NavLink>
<NavLink to="/about" activeClassName="activeNavButton">About</NavLink>

Although the past week was tough, I'm enjoying React overall. Looking forward to pushing through and building an awesome project in the upcoming Build Week!

← back to all posts