Dynamic route segments in NextJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a dynamic route file for a user profile page.

NextJS

pages/[1].js

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

A{userId}

BuserId

C(userId)

D[userId]

Attempts:

3 left

💡 Hint

Common Mistakes

Using curly braces or parentheses instead of square brackets.

Not using any brackets, which creates a static route.

In Next.js, dynamic route segments are defined by square brackets around the segment name, like [userId].

2fill in blank

medium

Complete the React component to access the dynamic route parameter using Next.js hooks.

NextJS

import { useRouter } from 'next/router';

export default function Profile() {
  const router = useRouter();
  const [1] = router.query.userId;

  return <p>User ID: {userId}</p>;
}

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

Aparams

Bid

CuserId

DqueryId

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different variable name than the dynamic segment.

Trying to destructure router.query incorrectly.

The dynamic route parameter is accessed from router.query using the exact segment name, here userId.

3fill in blank

hard

Fix the error in the dynamic route component to correctly handle the case when the router is not ready.

NextJS

import { useRouter } from 'next/router';

export default function Post() {
  const router = useRouter();
  if (!router.isReady) return <p>Loading...</p>;
  const postId = router.query.[1];
  return <p>Post ID: {postId}</p>;
}

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

Aid

BpostId

Cslug

Dpost

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different name than the dynamic segment in the query.

Not checking if the router is ready before accessing query.

The dynamic segment name must match the file name. If the file is [postId].js, then use router.query.postId.

4fill in blank

hard

Fill all three blanks to create a dynamic route segment and access its parameter in the component.

NextJS

import { useRouter } from 'next/router';

export default function Product() {
  const router = useRouter();
  const [1] = router.query.[2];
  return <p>Product ID: {productId}</p>;
}

// File path: pages/[3].js

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

AproductId

Bid

C[productId]

Dproduct

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for the file and query parameter.

Not using square brackets in the file name.

The dynamic segment and the query parameter must have the same name, here productId.

5fill in blank

hard

Fill all three blanks to create a nested dynamic route and access both parameters in the component.

NextJS

import { useRouter } from 'next/router';

export default function Review() {
  const router = useRouter();
  const [1] = router.query.[2];
  const [3] = router.query.reviewId;
  return <p>Product: {productId}, Review: {reviewId}</p>;
}

// File path: pages/products/[productId]/reviews/[reviewId].js

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

AproductId

CreviewId

Did

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up parameter names or missing one.

Not matching the dynamic segment names exactly.

The nested dynamic route uses [productId] and [reviewId]. Access both from router.query with matching names.

Practice

1. In Next.js, what does a file named [id].js inside the pages folder represent?

easy

A. A configuration file for setting environment variables

B. A static page that only matches the URL /id

C. A special API route for handling requests with an id parameter

D. A dynamic route segment that matches any value in the URL at that position

Solution

1. Step 1: Understand Next.js routing conventions

   Files inside the pages folder define routes. Square brackets [] indicate dynamic segments.

2. Step 2: Interpret [id].js meaning

   The file [id].js matches any URL segment in that position and passes it as a parameter named id.

3. Final Answer:

   A dynamic route segment that matches any value in the URL at that position -> Option D

4. Quick Check:

   Dynamic route = [segment] [OK]

Hint: Square brackets mean dynamic URL part in Next.js routes [OK]

Common Mistakes:

• Thinking [id].js is a static page
• Confusing dynamic routes with API routes
• Assuming it matches only the literal 'id'

2. Which of the following is the correct syntax to define a dynamic route segment for a Next.js page that captures a username?

easy

A. pages/:username.js

B. pages/username.js

C. pages/[username].js

D. pages/{username}.js

Solution

1. Step 1: Recall Next.js dynamic route syntax

   Dynamic segments use square brackets around the parameter name inside the pages folder.

2. Step 2: Match syntax for username parameter

   The correct syntax is [username].js to capture the username dynamically.

3. Final Answer:

   pages/[username].js -> Option C

4. Quick Check:

   Dynamic segment uses [param] syntax [OK]

Hint: Use square brackets for dynamic route names [OK]

Common Mistakes:

• Using colon or curly braces instead of square brackets
• Naming the file without brackets for dynamic routes
• Confusing dynamic routes with static filenames

3. Given the file structure:
pages/blog/[slug].js
and the URL /blog/hello-world, what will be the value of the slug parameter inside the page component?

medium

A. "hello-world"

B. "blog"

C. "[slug]"

D. undefined

Solution

1. Step 1: Identify dynamic segment from file name

   The file [slug].js captures the URL segment after /blog/ as slug.

2. Step 2: Match URL segment to parameter

   For URL /blog/hello-world, the segment hello-world is assigned to slug.

3. Final Answer:

   "hello-world" -> Option A

4. Quick Check:

   URL segment after folder = slug value [OK]

Hint: Dynamic segment captures URL part matching filename [OK]

Common Mistakes:

• Using folder name as parameter value
• Assuming parameter is the literal filename
• Expecting undefined if parameter not explicitly passed

4. Consider this Next.js dynamic route file: pages/product/[id].js. Which of the following code snippets correctly accesses the id parameter inside the component?

medium

A. const router = useRouter(); const { id } = router.query;

B. const { id } = props.params;

C. const id = useParams().id;

D. const id = getIdFromUrl();

Solution

1. Step 1: Recall how to access route params in Next.js pages

   Next.js uses the useRouter hook from next/router to access query parameters.

2. Step 2: Identify correct syntax for extracting id

   The correct way is const router = useRouter(); const { id } = router.query;.

3. Final Answer:

   const router = useRouter(); const { id } = router.query; -> Option A

4. Quick Check:

   useRouter().query gives dynamic params [OK]

Hint: Use useRouter().query to get dynamic route params [OK]

Common Mistakes:

• Using props.params which is not standard in Next.js pages
• Using useParams() which is from React Router, not Next.js
• Calling undefined functions like getIdFromUrl()

5. You want to create a nested dynamic route in Next.js to handle URLs like /dashboard/user/123 where 123 is a user ID. Which file structure correctly implements this?

hard

A. pages/dashboard/[user]/[id].js

B. pages/dashboard/user/[id].js

C. pages/dashboard/[id].js

D. pages/[dashboard]/user/[id].js

Solution

1. Step 1: Analyze the URL structure

   The URL /dashboard/user/123 has three segments: dashboard, user, and a dynamic id.

2. Step 2: Match file structure to URL segments

   Static segments dashboard and user are folders, and [id].js captures the dynamic user ID.

3. Step 3: Verify options

   pages/dashboard/user/[id].js matches the folder structure exactly. Options B and D incorrectly treat static parts as dynamic. pages/dashboard/[id].js misses the user folder.

4. Final Answer:

   pages/dashboard/user/[id].js -> Option B

5. Quick Check:

   Static folders + [id].js for dynamic segment [OK]

Hint: Match URL parts to folders; dynamic parts use [param].js [OK]

Common Mistakes:

• Making static parts dynamic segments
• Omitting intermediate folders for static URL parts
• Confusing order of folders and dynamic files