Why data fetching differs in Next.js - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to fetch data on the server side in Next.js using the recommended method.

NextJS

export async function [1]() {
  const res = await fetch('https://api.example.com/data');
  const data = await res.json();
  return { props: { data } };
}

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

AgetStaticPaths

BuseEffect

CgetServerSideProps

DcomponentDidMount

Attempts:

3 left

💡 Hint

Common Mistakes

Using client-side hooks like useEffect for server-side data fetching.

Confusing getStaticPaths with data fetching functions.

In Next.js, getServerSideProps is used to fetch data on the server side at request time.

2fill in blank

medium

Complete the code to fetch static data at build time in Next.js.

NextJS

export async function [1]() {
  const res = await fetch('https://api.example.com/data');
  const data = await res.json();
  return { props: { data } };
}

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

AgetStaticProps

BuseEffect

CcomponentDidMount

DgetServerSideProps

Attempts:

3 left

💡 Hint

Common Mistakes

Using getServerSideProps when static generation is intended.

Trying to fetch data inside the component with useEffect for static pages.

getStaticProps fetches data at build time, generating static pages.

3fill in blank

hard

Fix the error in this Next.js page component by choosing the correct data fetching method.

NextJS

function Page({ data }) {
  return <div>{data.message}</div>;
}

export async function [1]() {
  const res = await fetch('https://api.example.com/data');
  const data = await res.json();
  return { props: { data } };
}

export default Page;

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

AgetStaticProps

BuseEffect

CcomponentDidMount

DgetServerSideProps

Attempts:

3 left

💡 Hint

Common Mistakes

Using client-side hooks as exported functions.

Confusing server-side and static generation methods.

The page uses static props, so getStaticProps is the correct method to fetch data at build time.

4fill in blank

hard

Fill both blanks to create a Next.js API route that returns JSON data.

NextJS

export default function handler(req, res) {
  if (req.method === '[1]') {
    res.status(200).json({ message: '[2]' });
  } else {
    res.status(405).end();
  }
}

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

AGET

BPOST

CHello from API

DData fetched

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase HTTP methods.

Returning non-JSON responses without proper headers.

API routes handle HTTP methods like GET. The message can be any string, here 'Hello from API'.

5fill in blank

hard

Fill all three blanks to fetch data in a React Server Component in Next.js 13+.

NextJS

import React from 'react';

async function fetchData() {
  const res = await fetch('[1]');
  return res.[2]();
}

export default async function Page() {
  const data = await fetchData();
  return <main><h1>[3]</h1></main>;
}

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

Ahttps://api.example.com/data

Bjson

CWelcome to Next.js

Dtext

Attempts:

3 left

💡 Hint

Common Mistakes

Using text() instead of json() for JSON data.

Leaving the heading blank or unrelated.

The fetch URL is the API endpoint, json() parses the response, and the heading displays a welcome message.

Practice

1. Why does Next.js use different methods for data fetching?

easy

A. Because Next.js only works with static data

B. Because Next.js does not support client-side data fetching

C. Because all data must be fetched only on the server

D. Because data can be fetched at different times for better performance

Solution

1. Step 1: Understand data fetching timing in Next.js

   Next.js allows fetching data before the page loads (server-side or static) or after the page loads (client-side).

2. Step 2: Recognize the reason for multiple methods

   Using different methods helps improve performance and user experience by choosing the best time to fetch data.

3. Final Answer:

   Because data can be fetched at different times for better performance -> Option D

4. Quick Check:

   Data fetching timing = A [OK]

Hint: Think when data is needed: before or after page loads [OK]

Common Mistakes:

• Assuming Next.js only fetches data on the server
• Believing client-side fetching is not supported
• Thinking all data must be static

2. Which of the following is the correct way to fetch data at build time in Next.js?

easy

A. export async function getStaticProps() { return { props: {} } }

B. export async function getServerSideProps() { return { props: {} } }

C. export async function fetchData() { return { props: {} } }

D. export async function getClientSideProps() { return { props: {} } }

Solution

1. Step 1: Identify build-time data fetching method

   Next.js uses getStaticProps to fetch data at build time for static generation.

2. Step 2: Compare options with Next.js conventions

   getServerSideProps is for server-side rendering, not build time; others are invalid function names.

3. Final Answer:

   export async function getStaticProps() { return { props: {} } } -> Option A

4. Quick Check:

   Build-time fetch = getStaticProps A [OK]

Hint: Remember: Static = getStaticProps, Server = getServerSideProps [OK]

Common Mistakes:

• Confusing getServerSideProps with getStaticProps
• Using incorrect function names
• Thinking client-side fetching uses special props functions

3. What will be the rendered output if you use getServerSideProps to fetch data that changes every second?

medium

A. The page shows the data as it was at build time

B. The page never updates after first load

C. The page shows the latest data on every request

D. The page shows an error because data changes too fast

Solution

1. Step 1: Understand getServerSideProps behavior

   This function runs on every request, so it fetches fresh data each time the page loads.

2. Step 2: Apply to data changing every second

   Since data changes frequently, getServerSideProps ensures the page always shows the latest data.

3. Final Answer:

   The page shows the latest data on every request -> Option C

4. Quick Check:

   Server-side fetch = fresh data B [OK]

Hint: Server-side fetch updates on every request [OK]

Common Mistakes:

• Thinking getServerSideProps caches data at build time
• Assuming data never updates after first load
• Believing it causes errors with fast-changing data

4. Identify the error in this Next.js data fetching code:

export async function getStaticProps() {
  const res = await fetch('https://api.example.com/data')
  const data = await res.json()
  return { data }
}

medium

A. Missing return of props object wrapping data

B. fetch cannot be used inside getStaticProps

C. Async functions are not allowed in Next.js data fetching

D. The URL must be relative, not absolute

Solution

1. Step 1: Check return value format in getStaticProps

   Next.js expects an object with a props key containing the data, not just data alone.

2. Step 2: Identify the missing wrapper

   The code returns { data } but should return { props: { data } } for Next.js to pass props correctly.

3. Final Answer:

   Missing return of props object wrapping data -> Option A

4. Quick Check:

   Return props object = C [OK]

Hint: Always return { props: { ... } } in getStaticProps [OK]

Common Mistakes:

• Returning data directly without props wrapper
• Thinking fetch is disallowed in getStaticProps
• Believing async functions are forbidden

5. You want to show user-specific data that updates frequently but also want fast initial page load in Next.js. Which approach best fits this need?

hard

A. Use getStaticProps to fetch data and revalidate every second

B. Use getStaticProps for static data and fetch user data client-side after load

C. Fetch all data client-side only after page loads

D. Use getServerSideProps to fetch data on every request

Solution

1. Step 1: Analyze requirements for fast initial load and frequent updates

   Static data can be fetched at build time for fast load; user-specific data changes often and should be fetched client-side.

2. Step 2: Evaluate options

   Use getStaticProps to fetch data and revalidate every second revalidates too frequently and may cause performance issues; Use getServerSideProps to fetch data on every request delays initial load; Fetch all data client-side only after page loads delays all data; Use getStaticProps for static data and fetch user data client-side after load balances fast load and fresh user data.

3. Final Answer:

   Use getStaticProps for static data and fetch user data client-side after load -> Option B

4. Quick Check:

   Static + client fetch = D [OK]

Hint: Combine static build with client fetch for user data [OK]

Common Mistakes:

• Using only server-side fetching causing slow load
• Fetching everything client-side causing blank initial page
• Overusing revalidation causing unnecessary server load