jerrystsai / practice-for-week-14-react-router-navigation

Practice: Navigation

In this practice you will learn how to create navigation for your Route paths using Link and NavLink.

Setup

Click the Download Project button at the bottom of this page to go to the starter repo, then load the repo into CodeSandbox.

Navigation

In your App.js file, import the Link component from react-router-dom. You will use this component instead of the <a> element to which you are accustomed.

Beneath the h1 create a nav element with 2 classes: comp and nav. Inside the nav element, add an unordered list element. Add a list-item element inside the unordered list element. Now use the Link component to create a clickable link to the Home path. The child text inside the Link component should say 'Home'.

In your sandbox browser, you should now see a Navbar with the Home link.

Compare Link and anchor

In order to really understand why you are using the Link component, you should add an anchor tag to your code and view the difference.

Above your Home <li>, add an <li> with an anchor tag nested inside. The href should lead to the movies component (/movies) and have a child text of Anchor.

In your sandbox browser, click the Open In New Window button. Open the DevTools in the new window to the Elements tab. Expand the html tree as much as you can. Now, click on the anchor tag and notice how the whole page refreshes. Reopen the tree in the Elements tab. This time, click on the Home link and notice that only the component that has been mounted changes; the page itself does not refresh.

NavLink

You will now add the other links to your App.js. However, you also want to see a difference between the active link and the other links. To achieve that differentiation, you can use the NavLink component. (Remember that NavLink is just the Link component with extra functionality.)

Replace the Link import with the NavLink import.

Also, for your Home link, replace Link with NavLink. You will need to make your URL exact in this component, just as you did in the Route.

Now add list-items and NavLinks for the Stocks and Movies routes.

Take a look in your sandbox browser. Notice that the active link is now red? Your index.css defines an active class. NavLink automatically sees this and applies it to the active link. Click each item and notice how the link changes.

activeClassName and activeStyle

Now you are going to change the class that is called on the active link using the activeClassName attribute. Note that index.css also defines a purple class. In your App.js, add activeClassName='purple' to each NavLink. Your active link in the browser should now have a purple border around it.

Next, inside your NavLinks, use the activeStyle attribute. It works the same way that inline styling works for CSS. Add activeStyle={{ fontWeight: 'bold' }} to each NavLink. When you go to the browser, you should notice that each active link now has both a border and a bold font.

Redirect

Sometimes you want to allow access to a component only when a user is logged in. Otherwise, you want to navigate the user in another direction. Using the Redirect component can help you do this.

In your App.js file, just above the 'Page Not Found' route, add a Route that looks like this:

<Route path='/not-logged-in'>
  <h1> You Must Be Logged In To Enter.</h1>
</Route>

Next, in your Stocks/index.js file, create a variable called loggedIn and assign it to false.

Add an if statement that uses the Redirect component--don't forget to import it!--to redirect the user to the /not-logged-in URL when the loggedIn variable is false.

Test your code in the sandbox browser by clicking on the Stocks link. It should redirect you to the /not-logged-in route.

In Stocks/index.js, change the loggedIn variable to true. Now when you click on the Stocks link, you should see the Stocks component.

History API & useHistory hook for navigation

You can use the useHistory hook to navigate after some transaction has taken place. In this case, your goal is to navigate back to Home after a user clicks a button in the Stocks component.

First, under the h1 tag in your Stocks JSX, create a button with an onClick event listener that looks like this:

  <button onClick={handleClick}>Home</button>

Event listeners differ in React in that the event listener is camelCased and will always be assigned to a function.

Here you have set the onClick event to invoke the function handleClick, but you have not written handleClick yet.

Above the return, create a function called handleClick. It should alert the user with a message and then navigate home.

  const handleClick = () => {
    window.alert('Sending info to the DB!');
  };

Test in the sandbox browser.

Now you want to redirect after you click the ok button in the alert box.

Import the useHistory hook from react-router-dom.

In your component, invoke the useHistory hook and assign it to a new variable called history.

If you are curious about what you will receive in the history variable, log it and take a look in the browser DevTools.

After the window.alert in the handleClick function, use the .push method on the history object to navigate the user to the Home component.

Test in the browser.

What you have learned

Congratulations! In this practice you have learned how to

1. Navigate to another address with the Link component
2. Use the NavLink component's added capability to set the active class in CSS
3. Personalize the active links with specialized NavLink attributes
4. Navigate the user to another location using Redirect
5. Use the History API and the useHistory hook to navigate the user to another location after they have handled some other functionality