Why Conditional routes in NextJS? - Purpose & Use Cases

The Big Idea

Discover how to keep your app secure and smooth without messy code everywhere!

The Scenario

Imagine building a website where some pages should only be seen by logged-in users, and others by guests. You try to check user status on every page manually and redirect them yourself.

The Problem

Manually checking user status and redirecting on every page is tiring and easy to forget. It leads to bugs where users see pages they shouldn't or get stuck in loops. It also clutters your code with repeated checks everywhere.

The Solution

Conditional routes let you define rules once that control who can see which pages. The framework handles the checks and redirects automatically, keeping your code clean and your app secure.

Before vs After

✗ Before

if (!user) { router.push('/login') } // on every page

✓ After

export const routes = [{ path: '/dashboard', authRequired: true }]; // centralized rules

What It Enables

Conditional routes make it easy to control access and navigation based on user state, improving security and user experience.

Real Life Example

A shopping site shows the cart page only to logged-in users and redirects guests to sign in automatically.

Key Takeaways

Manual route checks are repetitive and error-prone.

Conditional routes centralize access control logic.

This leads to cleaner code and safer navigation.

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