Server state vs client state in NextJS - Practice Questions

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Server State vs Client State in Next.js

In Next.js, which of the following best describes server state compared to client state?

A Server state is data fetched and rendered on the server before sending HTML to the client, while client state is data managed and updated within the browser after page load.

B Server state is data stored only in the browser's memory, while client state is data fetched from external APIs on the server.

C Server state and client state are the same; both refer to data stored in React components on the client side.

D Server state is data that never changes, while client state is data that changes only on the server.

💡 Hint

Think about where the data lives and when it is fetched or updated.

Server state is data fetched on the server (e.g., via getServerSideProps) and sent as HTML to the client. Client state is data managed inside the browser, often with React hooks like useState, and can change without a full page reload.

❓ component_behavior

intermediate

Next.js Component Behavior with Server and Client State

Consider a Next.js page that fetches a list of products on the server and also allows users to filter products on the client. Which statement best describes how server and client state work together here?

A Filtering updates the server state directly without any client-side changes.

B Filtering triggers a full server reload to update the product list each time the user changes the filter.

C The product list is fetched on the server and passed as props; filtering happens in client state without refetching from the server.

D The product list is fetched on the client only after the page loads; server state is not used.

💡 Hint

Think about how initial data is loaded and how user interactions update the UI.

Next.js fetches the product list on the server and sends it as props. The client manages filtering locally using React state, so no extra server fetch is needed for filtering.

📝 Syntax

advanced

Identifying Server State Fetching in Next.js

Which of the following Next.js code snippets correctly fetches server state during server-side rendering?

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

// Which data fetching method is correct?

A

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

B

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

C

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

D

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

💡 Hint

Look for the official Next.js data fetching method that runs on the server for every request.

getServerSideProps runs on the server on every request and fetches data to pass as props. getStaticProps runs at build time, and getClientSideProps does not exist.

🔧 Debug

advanced

Debugging Client State Update in Next.js

Given this React component in Next.js, what is the main reason the counter does not update on button click?

import { useState } from 'react';

export default function Counter() {
  const [count, setCount] = useState(0);

  function handleClick() {
    count = count + 1;
  }

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={handleClick}>Increment</button>
    </div>
  );
}

A The code tries to assign directly to the state variable instead of using the setter function, so React does not re-render.

B The useState hook is missing an initial value, causing the state to be undefined.

C The handleClick function is not bound to the button's onClick event properly.

D React components cannot update state inside event handlers.

💡 Hint

Remember how React state variables should be updated.

React state variables are read-only. To update state, you must call the setter function returned by useState. Direct assignment to the state variable does not trigger re-render.

❓ state_output

expert

Output of Mixed Server and Client State in Next.js

What will be the rendered output of this Next.js page after the user clicks the button once?

import { useState } from 'react';

export async function getServerSideProps() {
  return { props: { initialCount: 5 } };
}

export default function Page({ initialCount }) {
  const [count, setCount] = useState(initialCount);

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>Increment</button>
    </div>
  );
}

A Count: 5

B Count: 6

C Count: 1

D Count: 0

💡 Hint

Consider the initial state from server props and what happens after clicking the button.

The initial count is 5 from server props. Clicking the button calls setCount(count + 1), so the count updates to 6 and re-renders.