React Libraries

Joel Ross

React Libraries

Joel Ross

React Libraries

React components are structured to be self-contained, re-usable elements... so there are lots of pre-defined components online you can use!

In order to use a component in your app:

Find it! (via npm, google, etc). Read the documentation
Install it! npm install lib-name
Import it! import { ComponentName } from 'lib-name'
- (import structure may vary per library)
Render it! <ComponentName />
- Remember to pass any expected props!

React Router

Joel Ross

Our chat app so far...

Single-Page Applications

https://drive.google.com/drive/my-drive

Client-Side Routing

Render a different component depending on the URL.

"IF the current url MATCHES a route, render this Component!"

function App(props) {
  //pick a component based on the URL
  let componentToRender = null;
  if(currentUrl === '/home'){ //pseudocode comparison with URL
    componentToRender = <HomePage />;
  }
  else if(currentUrl === '/about'){
    componentToRender = <AboutPage />;
  }

  //render that component
  return <div>{componentToRender}</div>;
}

`react-router`

A library of React Components that can determine which other components to render based on the current URL.

Install Library

Import Components

//in App.js
import { Routes, Route } from 'react-router-dom';

# Install library (on command line)
npm install react-router-dom

https://reactrouter.com/docs/en/v6

as of Nov 2021

Router Versions

The version we're targeting:

Adds data apis (not using)

(other changes since then are mostly not relevant for us)

BrowserRouter

The BrowserRouter component will keep track of the current URL in its state, and re-renders descendent components if that changes.

//index.js

import { BrowserRouter } from 'react-router-dom'
import App from './components/App.js'

//render the App *inside* of the BrowserRouter
const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(
  <BrowserRouter>
    <App />
  </BrowserRouter>
);

Routes

Pass elements in a Route Component to specify that they should only render when the URL matches a particular path. All routes go inside of a Routes element, which chooses which to "match" based on the URL

function App(props) {
  return (
    <Routes> {/* the collection of routes to match */}
      {/* if currentUrlPath === "home" */}
      <Route path="home" element={<HomePage />} />

      {/* else if currentUrlPath === "about" */}
      <Route path="about" element={<AboutPage />} />
    </Routes>
  );
}

Links

Use a Link element (in place of an <a>) to create state-based links between routes.

function Nav() {
  return (
    <nav>
      <ul>
        <li>
          {/* replaces anchor element */}
    	  <Link to="home">Home</Link>
        </li>
        <li>
          <Link to="about">About</Link>
        </li>
      </ul>
    </nav>
  );
}

URL Format

Like postal addresses, URLs follow a particular format.

scheme (protocol) how to access the information
domain which web service has the resource
path what resource to access
query extra parameters (arguments) to the request

format: ?key=value&key=value&key=value

Naming Routes

The web is based on the REST architecture. In this structure, each route (identifier, URI) should refer to a unique resource (set of information).

Think about what "information" should be found at each route. Come up with your routes first, and decide the components second!

function App(props) {
  return (
    <Routes>
      {/* good routes */}
      <Route path="/products" element={<AllProductsPage />} />
      <Route path="/products/hat" element={<HatPage />} />
      <Route path="/products/shoes" element={<ShoesPage />} />
      <Route path="/account" element={<AccountPage />} />
        
      {/* less good route -- an action, not a resource! */}
	  {/* (bad component definition as well) */}
      <Route path="/purchase" element={<ProcessPurchase />} />
    </Routes>
  )
}

Nesting Routes

The Route path corresponds to a segment of a URL, with nested Route elements corresponding to each segment. Nested Routes will render in place of an Outlet component

function App(props) {
  return (
    <Routes>
      <Route path="user" element={<UserLayout />} >
        <Route path="profile" element={<UserProfile />} />
        <Route path="favorites" element={<FavoriteItems />} />
      </Route>
      <Route path="items" element={<ItemList />} />
    </Routes>  
  );
}

function UserLayout(props) {
  render (
    <div className="user-layout">
      <h1>User Page</h1>
      <p>Layout specific content...</p>
      <Outlet /> {/* will be replaced with <UserProfile/>, etc */}
    </div>
  )
}

Protected Routes

A common use of nested routes is to make some routes protected, only showing content if e.g., the user is logged in.

function RequireAuth(props) {
  //...determine if user is logged in
  if(!userIsLoggedIn) { //if no user, say so
    return <p>Forbidden!</p>
  }
  else { //otherwise, show the child route content
    return <Outlet />
  }
}

function App(props) {
  return (
    <Routes>
      {/* protected routes */}
      <Route element={<RequireAuth />}>
        <Route path="profile" element={<ProfilePage />} />
        <Route path="secret" element={<SecretPage />} />
      </Route>
      {/* public routes */}
      <Route path="signin" element={<SignInPage />} />
    </Routes>
  )
}

"Variable" Routes

Sometimes you have a multiple routes that show the same component, just for different data--where that data is specified by one of the segments!

function App(props) {
  return (
    <Routes>
      <Route path="/products" element={<AllProductsPage />} />

      {/* routes go to same "view", just different content based on url */}
      <Route path="/products/hat" element={<ProductDetails item={"hat"} />} />
      <Route path="/products/shoes" element={<ProductDetails item={"shoes"} />} />

	</Routes>
  )
}

A url parameter is a "variable" in the url's path. This is a shortcut for defining a large number of routes that point to (similar) resources.

URL parameters are different than query params

URL Parameters

/users/:username

/users/:username/repos

/orgs/:owner/:repo

/users/{username}/repos

A variable

Two variables

Alternate notation

URL Params

Use :param syntax in the path to specify URL parameters. The useParams() hook lets you access the value of those parameters in the rendered element.

function App(props) {
  return (
    <Routes>
      {/* if currentUrl == "posts/______" */}
      {/* the string in the "blank" portion will be the
        * `postId` param */}
      <Route path="posts/:postId" element={<BlogPost />} />
    </Routes>
  );
}

import { useParams } from 'react-router-dom';

function BlogPost(props) {
  const urlParams = useParams(); //access the URL params as an object
  const postId = urlParams.postId; //can use destructuring instead
    
  return (
    {/* postId was the URL parameter from above! */}
    <h1>You are looking at blog post {urlParams.postId}</h1>
  )
}

Firebase Hosting

Joel Ross

Hosting on Firebase

GitHub pages is not able to cleanly handle client-side routing, so we'll use Firebase to host your projects instead!

Firebase is a web backend solution; it provides multiple features which you can access without need to "code" them yourselves.

Web Hosting
Databases
User Authentication

next weeks

React Deployment to Firebase

Use a combination of firebase command line tools and create-react-app scripts to build and deploy your React application to Firebase hosting!

https://create-react-app.dev/docs/deployment/#firebase