Modal pattern with intercepting routes in NextJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the Next.js router hook needed to handle route changes.

NextJS

import { [1] } from 'next/router';

Drag options to blanks, or click blank then click option'

AuseRouter

BusePathname

CuseRoute

DuseSearchParams

Attempts:

3 left

💡 Hint

Common Mistakes

Using usePathname instead of useRouter

Trying to import a hook that doesn't exist

The useRouter hook is used to programmatically navigate and intercept routes in Next.js.

2fill in blank

medium

Complete the code to define a modal component that uses state to control its visibility.

NextJS

import { useState } from 'react';

export default function Modal() {
  const [isOpen, [1]] = useState(false);
  return isOpen ? <div role="dialog">Modal Content</div> : null;
}

Drag options to blanks, or click blank then click option'

AopenModal

BsetOpen

CtoggleOpen

DsetIsOpen

Attempts:

3 left

💡 Hint

Common Mistakes

Using a setter name that doesn't match the state variable

Using a function name that implies toggling instead of setting

The setter function for isOpen state is conventionally named setIsOpen.

3fill in blank

hard

Fix the error in the code to correctly intercept route changes and open the modal.

NextJS

import { useRouter } from 'next/router';
import { useState, useEffect } from 'react';

export default function Page() {
  const router = useRouter();
  const [modalOpen, setModalOpen] = useState(false);

  useEffect(() => {
    const handleRouteChange = (url) => {
      if (url.includes('modal')) {
        setModalOpen(true);
      } else {
        setModalOpen(false);
      }
    };

    router.events.[1]('routeChangeStart', handleRouteChange);

    return () => {
      router.events.off('routeChangeStart', handleRouteChange);
    };
  }, [router]);

  return modalOpen ? <div role="dialog">Modal Open</div> : <div>Main Page</div>;
}

Drag options to blanks, or click blank then click option'

Aon

BaddListener

CaddEventListener

DonRouteChangeStart

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'addEventListener' which is for DOM events

Using 'addListener' which does not exist

In Next.js Pages Router, the router's event emitter uses router.events.on to listen for routeChangeStart events.

4fill in blank

hard

Fill both blanks to create an intercepting route link that opens the modal without full page reload.

NextJS

import Link from 'next/link';

export default function Home() {
  return (
    <Link href="/modal" [1]=[2]>
      Open Modal
    </Link>
  );
}

Drag options to blanks, or click blank then click option'

Areplace

Bprefetch

Ctrue

Dshallow

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'replace' or 'prefetch' which do different things

Not passing the boolean true as a value

The shallow prop with value true allows route changes without full reload, useful for modals.

5fill in blank

hard

Fill the blanks to correctly implement a modal that closes on backdrop click and updates the route.

NextJS

import { useRouter } from 'next/router';

export default function Modal() {
  const router = useRouter();

  function closeModal() {
    router.[1]('/');
  }

  return (
    <div role="dialog" onClick={closeModal} aria-modal="true">
      <div onClick={e => e.[2]()}>
        Modal Content
        <button onClick={closeModal} aria-label="Close modal">Close</button>
      </div>
    </div>
  );
}

Drag options to blanks, or click blank then click option'

Apush

BstopPropagation

CpreventDefault

Dreplace

Attempts:

3 left

💡 Hint

Common Mistakes

Using push instead of replace for route update

Not stopping event propagation causing modal to close immediately

Use replace to update the route without adding history entry, stopPropagation to prevent closing modal when clicking inside. push and preventDefault are distractors here.

Practice

1. What is the main benefit of using the modal pattern with intercepting routes in Next.js?

easy

A. It automatically reloads the entire page when opening a modal.

B. It allows showing a popup without leaving the current page.

C. It disables keyboard navigation while the modal is open.

D. It prevents any URL changes when interacting with the modal.

Solution

1. Step 1: Understand modal with intercepting routes

   This pattern lets you open a modal that overlays the current page content without navigating away.

2. Step 2: Identify the benefit

   Because the modal is shown on top, the user stays on the same page, improving user experience.

3. Final Answer:

   It allows showing a popup without leaving the current page. -> Option B

4. Quick Check:

   Modal pattern = popup without page change [OK]

Hint: Modals with intercepting routes keep you on the same page [OK]

Common Mistakes:

• Thinking the page reloads when modal opens
• Assuming URL never changes
• Believing keyboard navigation is disabled

2. Which Next.js feature is commonly used to control modal visibility with intercepting routes?

easy

A. Using URL query parameters to toggle modal state

B. Using React class components with state

C. Using server-side rendering to open modals

D. Using CSS hover effects to show modals

Solution

1. Step 1: Identify modal control method

   Next.js modals with intercepting routes often use URL query parameters to track if modal is open or closed.

2. Step 2: Eliminate incorrect options

   React class components are outdated; server-side rendering doesn't control modal visibility dynamically; CSS hover is unrelated to routing.

3. Final Answer:

   Using URL query parameters to toggle modal state -> Option A

4. Quick Check:

   Modal visibility = URL query param [OK]

Hint: Modal open state is often in URL query parameters [OK]

Common Mistakes:

• Confusing client state with URL state
• Using class components instead of hooks
• Relying on CSS hover for modal control

3. Given this Next.js snippet controlling a modal with query param ?modal=open:

const router = useRouter();
const isModalOpen = router.query.modal === 'open';

return (
  <>
    {isModalOpen && <ModalComponent />}
    <MainPageContent />
  </>
);

What happens when the URL changes from /page to /page?modal=open?

medium

A. The page reloads and shows a blank screen.

B. The main page content is replaced by the modal component.

C. Nothing changes because query parameters don't affect rendering.

D. The modal component appears over the main page content.

Solution

1. Step 1: Understand the code logic

   The code checks if the query parameter 'modal' equals 'open'. If yes, it renders the modal component alongside the main content.

2. Step 2: Analyze URL change effect

   Changing URL to include '?modal=open' sets isModalOpen true, so modal appears over the main page without replacing it.

3. Final Answer:

   The modal component appears over the main page content. -> Option D

4. Quick Check:

   Query param 'modal=open' = modal visible [OK]

Hint: Query param 'modal=open' triggers modal display [OK]

Common Mistakes:

• Thinking modal replaces main content
• Ignoring query parameters in rendering
• Assuming page reloads on query change

4. Consider this Next.js modal code snippet:

const router = useRouter();
const isModalOpen = router.query.modal === 'open';

function closeModal() {
  router.push('/page');
}

return (
  <>
    {isModalOpen && <Modal onClose={closeModal} />}
    <PageContent />
  </>
);

What is a likely bug in this code regarding accessibility?

medium

A. The URL does not update when the modal opens.

B. The modal never closes because router.push is incorrect.

C. Keyboard focus is not moved to the modal when it opens.

D. The modal content is rendered outside the React tree.

Solution

1. Step 1: Review modal accessibility needs

   When a modal opens, keyboard focus should move inside it for screen reader and keyboard users.

2. Step 2: Check code for focus management

   The code changes URL and renders modal but does not handle moving keyboard focus to modal.

3. Final Answer:

   Keyboard focus is not moved to the modal when it opens. -> Option C

4. Quick Check:

   Modal accessibility = move keyboard focus [OK]

Hint: Always move keyboard focus into modal on open [OK]

Common Mistakes:

• Ignoring keyboard focus management
• Assuming URL push closes modal automatically
• Confusing rendering with accessibility

5. You want to implement a modal in Next.js that opens on /gallery?modal=photo123 and closes by removing the query param, without losing the gallery scroll position. Which approach best achieves this?

hard

A. Use router.push with shallow: true to update URL without full reload and keep scroll.

B. Use router.replace without shallow to reload page and reset scroll.

C. Use window.location.href to change URL and force reload.

D. Use CSS to hide modal and ignore URL changes.

Solution

1. Step 1: Understand shallow routing in Next.js

   Shallow routing updates the URL without running data fetching methods or reloading the page, preserving scroll and state.

2. Step 2: Apply shallow routing to modal open/close

   Using router.push with shallow: true changes query params to open/close modal without losing scroll position.

3. Final Answer:

   Use router.push with shallow: true to update URL without full reload and keep scroll. -> Option A

4. Quick Check:

   Shallow routing = URL change without reload [OK]

Hint: Use shallow routing to keep scroll when changing URL [OK]

Common Mistakes:

• Using router.replace without shallow reloads page
• Using window.location.href causes full reload
• Ignoring URL for modal state control