Conditional routes in NextJS - Mini Project: Build & Apply

Conditional Routes in Next.js

📖 Scenario: You are building a simple Next.js app that shows different pages based on whether a user is logged in or not. This is common in real websites where some pages are private and others are public.

🎯 Goal: Create a Next.js app with conditional routing that shows a Login page if the user is not logged in, and a Dashboard page if the user is logged in.

📋 What You'll Learn

Create a boolean variable isLoggedIn to represent user login status

Create two simple components: Login and Dashboard

Use conditional rendering in the main page to show Login if isLoggedIn is false

Show Dashboard if isLoggedIn is true

💡 Why This Matters

🌍 Real World

Many websites show different pages or content depending on whether a user is logged in. This project shows how to do that simply in Next.js.

💼 Career

Understanding conditional routes and rendering is essential for building user-friendly web apps that handle authentication and private content.

1

Set up login status variable

Create a boolean variable called isLoggedIn and set it to false to represent that the user is not logged in yet.

NextJS

# Create a boolean variable isLoggedIn and set it to false
# Your code here

Hint

Use const isLoggedIn = false; to create the variable.

2

Create Login and Dashboard components

Create two React functional components called Login and Dashboard. Each should return a simple <div> with text: "Please log in" for Login and "Welcome to your dashboard" for Dashboard.

NextJS

const isLoggedIn = false;

// Create Login component
// Your code here

// Create Dashboard component
// Your code here

Hint

Define two functions: function Login() { return <div>Please log in</div>; } and similarly for Dashboard.

3

Add conditional rendering in main component

Create a React functional component called HomePage. Inside it, use isLoggedIn to conditionally render the Dashboard component if isLoggedIn is true, or the Login component if isLoggedIn is false.

NextJS

const isLoggedIn = false;

function Login() {
  return Please log in;
}

function Dashboard() {
  return Welcome to your dashboard;
}

// Create HomePage component with conditional rendering
// Your code here

Hint

Use a ternary operator inside the return of HomePage to choose which component to show.

4

Export HomePage as default

Add a default export for the HomePage component so Next.js can use it as the main page.

NextJS

const isLoggedIn = false;

function Login() {
  return Please log in;
}

function Dashboard() {
  return Welcome to your dashboard;
}

function HomePage() {
  return isLoggedIn ?  : ;
}

// Export HomePage as default
// Your code here

Hint

Use export default HomePage; at the end of the file.

Practice

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

easy

A. To create static pages only

B. To style pages differently

C. To fetch data from an API

D. To control access and redirect users based on conditions

Solution

1. Step 1: Understand conditional routes concept

   Conditional routes let you decide which users can see certain pages or redirect them elsewhere.

2. Step 2: Identify the purpose in Next.js

   Next.js uses conditional routes mainly to protect pages or redirect users based on login or roles.

3. Final Answer:

   To control access and redirect users based on conditions -> Option D

4. Quick Check:

   Conditional routes = control access [OK]

Hint: Think: Who should see this page? Redirect if no permission. [OK]

Common Mistakes:

• Confusing conditional routes with styling or data fetching
• Thinking conditional routes create static pages
• Believing conditional routes only fetch data

2. Which Next.js hook is commonly used to perform client-side redirects in conditional routes?

easy

A. useState

B. useEffect

C. useRouter

D. useContext

Solution

1. Step 1: Identify hooks for routing

   Next.js provides useRouter to access routing methods like push for redirects.

2. Step 2: Confirm redirect usage

   While useEffect runs side effects, useRouter is needed to actually change routes.

3. Final Answer:

   useRouter -> Option C

4. Quick Check:

   Redirects use useRouter [OK]

Hint: Redirects need router methods, so useRouter is key. [OK]

Common Mistakes:

• Using useState to redirect (it manages state only)
• Confusing useEffect as the hook that changes routes
• Thinking useContext handles routing

3. Given this Next.js component, what will happen if isLoggedIn is false?

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

export default function Dashboard() {
  const router = useRouter();
  const isLoggedIn = false;

  useEffect(() => {
    if (!isLoggedIn) {
      router.push('/login');
    }
  }, [isLoggedIn]);

  return <h1>Dashboard</h1>;
}

medium

A. The user is redirected to the /login page

B. The page reloads infinitely

C. The page shows an error

D. The user stays on the Dashboard page

Solution

1. Step 1: Analyze the useEffect condition

   The effect checks if isLoggedIn is false, then calls router.push('/login').

2. Step 2: Understand router.push behavior

   This causes a client-side redirect to the login page when not logged in.

3. Final Answer:

   The user is redirected to the /login page -> Option A

4. Quick Check:

   False login triggers redirect [OK]

Hint: False login triggers router.push to /login. [OK]

Common Mistakes:

• Thinking the user stays on Dashboard despite redirect
• Assuming an error occurs without redirect
• Believing infinite reload happens here

4. Identify the error in this Next.js conditional route code:

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

export default function Profile() {
  const router = useRouter();
  const isAuthorized = false;

  if (!isAuthorized) {
    router.push('/unauthorized');
  }

  return <h1>Profile</h1>;
}

medium

A. Calling router.push inside the component body causes an error

B. Missing dependency array in useEffect

C. useRouter is not imported correctly

D. The component returns invalid JSX

Solution

1. Step 1: Check where router.push is called

   router.push is called directly inside the component body, which runs on every render and is not allowed.

2. Step 2: Correct usage with useEffect

   Redirects should be inside useEffect to avoid infinite loops or errors.

3. Final Answer:

   Calling router.push inside the component body causes an error -> Option A

4. Quick Check:

   Redirects must be inside useEffect [OK]

Hint: Put router.push inside useEffect, not directly in component body. [OK]

Common Mistakes:

• Calling router.push directly in component body
• Ignoring useEffect for side effects
• Assuming missing import causes error here

5. You want to create a Next.js page that only logged-in users can access. If the user is not logged in, redirect them to '/login'. Which is the best approach?

1. Use useRouter and useEffect to check login and redirect client-side.
2. Use Next.js middleware to check authentication before rendering.
3. Render a loading state while checking login status.
4. Avoid rendering protected content until login is confirmed.

Which combination correctly applies conditional routing best practice?

hard

A. Only 1 and 2

B. All 1, 2, 3, and 4

C. Only 2 and 4

D. Only 1, 3, and 4

Solution

1. Step 1: Understand client-side and server-side checks

   Client-side redirect with useRouter/useEffect (1) is common, but middleware (2) adds server-side protection.

2. Step 2: Consider user experience

   Showing a loading state (3) and avoiding rendering protected content before login confirmation (4) improve UX and prevent flicker.

3. Step 3: Combine all for best practice

   Using all four ensures secure, smooth conditional routing in Next.js.

4. Final Answer:

   All 1, 2, 3, and 4 -> Option B

5. Quick Check:

   Best practice = all steps combined [OK]

Hint: Combine client, server checks and loading states for best routing. [OK]

Common Mistakes:

• Relying only on client-side redirects
• Skipping loading states causing flicker
• Ignoring server-side middleware protection