Server-side state passing in NextJS

Introduction

Server-side state passing lets your Next.js app send data from the server to the page before it shows up. This helps show fresh info right away without waiting for the browser to ask for it.

You want to show user info right when the page loads, like a profile page.

You need to fetch data from a database or API before showing the page.

You want better SEO by sending content from the server.

You want to avoid loading spinners by having data ready on page load.

Syntax

NextJS

export async function getServerSideProps(context) {
  // fetch or prepare data here
  const data = 'some data';
  return {
    props: { data }, // pass data as props to the page
  };
}

export default function Page({ data }) {
  return <div>{data}</div>;
}

getServerSideProps runs on the server for every request.

The returned props object is sent to the page component as props.

Examples

This example sends a simple message from the server to the page.

NextJS

export async function getServerSideProps() {
  return { props: { message: 'Hello from server!' } };
}

export default function Page({ message }) {
  return <h1>{message}</h1>;
}

This example fetches data from an API on the server and passes it to the page.

NextJS

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

export default function Page({ data }) {
  return <pre>{JSON.stringify(data, null, 2)}</pre>;
}

Sample Program

This page shows the current server time when the page loads. The time is fetched on the server and passed as a prop.

NextJS

export async function getServerSideProps() {
  const currentTime = new Date().toLocaleTimeString();
  return { props: { currentTime } };
}

export default function TimePage({ currentTime }) {
  return (
    <main>
      <h1>Current Server Time</h1>
      <p>The time when this page was loaded is: {currentTime}</p>
    </main>
  );
}

Important Notes

getServerSideProps runs on every request, so it can slow down your page if it does heavy work.

Use server-side state passing when you need fresh data on each page load.

Remember this only works in page components, not in regular React components.

Summary

Server-side state passing sends data from the server to the page before it shows.

Use getServerSideProps to fetch or prepare data on the server.

This helps show fresh data immediately and improves SEO.

Practice

1. What is the main purpose of getServerSideProps in Next.js?

easy

A. To manage browser cookies

B. To handle client-side routing

C. To style components dynamically

D. To fetch data on the server before rendering the page

Solution

1. Step 1: Understand getServerSideProps role

   This function runs on the server before the page loads to fetch or prepare data.

2. Step 2: Identify its main use

   It ensures the page has fresh data on first load and improves SEO by server-side rendering.

3. Final Answer:

   To fetch data on the server before rendering the page -> Option D

4. Quick Check:

   Server-side data fetching = A [OK]

Hint: Remember: server-side means before page shows [OK]

Common Mistakes:

• Confusing client-side routing with server-side data fetching
• Thinking it styles components
• Assuming it manages cookies directly

2. Which of the following is the correct syntax to export getServerSideProps in a Next.js page?

easy

A. export default getServerSideProps = () => ({ props: {} })

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

C. function getServerSideProps() { return props: {} }

D. export getServerSideProps = async () => { return {} }

Solution

1. Step 1: Recall correct export syntax

   getServerSideProps must be an async function exported with the exact name.

2. Step 2: Check return structure

   It returns an object with a props key containing data for the page.

3. Final Answer:

   export async function getServerSideProps(context) { return { props: {} } } -> Option B

4. Quick Check:

   Correct async export with props = D [OK]

Hint: Use async function with named export and return props [OK]

Common Mistakes:

• Using arrow function without export keyword
• Returning object without wrapping props
• Using default export incorrectly

3. Given this code snippet in a Next.js page, what will be the rendered output?

export async function getServerSideProps() {
  return { props: { message: 'Hello from server' } };
}

export default function Page({ message }) {
  return <h1>{message}</h1>;
}

medium

A. <h1>Hello from server</h1>

B. Error: message is undefined

C. <h1>{message}</h1>

D. <h1>Hello from client</h1>

Solution

1. Step 1: Understand data flow

   getServerSideProps passes message as a prop to the page component.

2. Step 2: Render output

   The component receives message and renders it inside an <h1> tag.

3. Final Answer:

   <h1>Hello from server</h1> -> Option A

4. Quick Check:

   Server prop passed and rendered = A [OK]

Hint: Props from server appear as component parameters [OK]

Common Mistakes:

• Thinking props are undefined without client fetch
• Rendering literal {message} instead of value
• Confusing server message with client message

4. What is wrong with this getServerSideProps function?

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

medium

A. The returned props must be an object with a props key wrapping data

B. The fetch call is missing await

C. getServerSideProps cannot be async

D. The function should return data directly, not inside props

Solution

1. Step 1: Check fetch usage

   The fetch is awaited correctly, so no issue there.

2. Step 2: Check return structure

   The function must return an object with a props key containing an object. Here, data is returned directly, which is incorrect.

3. Final Answer:

   The returned props must be an object with a props key wrapping data -> Option A

4. Quick Check:

   Return { props: { ... } } not just data [OK]

Hint: Always wrap data inside props object in return [OK]

Common Mistakes:

• Returning data directly instead of inside props
• Forgetting to await fetch
• Thinking async is not allowed

5. You want to pass user data fetched from a database to a Next.js page using getServerSideProps. Which approach correctly handles the asynchronous fetch and passes the data safely to the page component?

hard

A. export async function getServerSideProps() {
const user = getUserFromDB();
return { props: user };
}

B. export function getServerSideProps() {
const user = getUserFromDB();
return { props: { user } };
}

C. export async function getServerSideProps() {
const user = await getUserFromDB();
return { props: { user } };
}

D. export async function getServerSideProps() {
const user = await getUserFromDB();
return user;
}

Solution

1. Step 1: Handle async data fetching

   The function must be async and await the database call to get user data.

2. Step 2: Return data wrapped in props object

   The returned object must have a props key containing an object with user data.

3. Final Answer:

   export async function getServerSideProps() { const user = await getUserFromDB(); return { props: { user } }; } -> Option C

4. Quick Check:

   Async await + return props object = C [OK]

Hint: Await async fetch and wrap result inside props [OK]

Common Mistakes:

• Not awaiting async database call
• Returning data directly without props wrapper
• Using non-async function for async fetch