Page.tsx as route definition in NextJS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What does this Next.js Page component render?

Consider this Next.js 14 Page.tsx file in the app directory. What will the user see when visiting this route?

NextJS

export default function Page() {
  return <main><h1>Welcome to Next.js 14!</h1><p>This is the home page.</p></main>;
}

A <main><h1>Welcome to Next.js 14!</h1><p>This is the home page.</p></main>

B <div><h1>Welcome to Next.js 14!</h1><p>This is the home page.</p></div>

C <main><h2>Welcome to Next.js 14!</h2><p>This is the home page.</p></main>

D <main><h1>Welcome!</h1><p>This is the home page.</p></main>

💡 Hint

Look carefully at the tags and text inside the returned JSX.

The component returns a

element with an

containing exactly 'Welcome to Next.js 14!' and a

with 'This is the home page.'. Only option A matches this exactly.

📝 Syntax

intermediate

Which option correctly exports a Next.js Page component in TypeScript?

Choose the correct way to define and export a Page component in Next.js 14 using TypeScript.

A export function Page() { return <div>Hello</div>; }

B export default const Page = () => <div>Hello</div>;

C function Page() { return <div>Hello</div>; } export Page;

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

💡 Hint

Next.js expects a default export for the page component.

Option D correctly defines and exports the Page component as the default export. Option D exports a named function, which Next.js does not recognize as a route. Option D has invalid export syntax. Option D has invalid syntax mixing export default and const.

❓ state_output

advanced

What is the rendered output after clicking the button?

This Next.js Page component uses React state. What text is shown after clicking the button once?

NextJS

import { useState } from 'react';

export default function Page() {
  const [count, setCount] = useState(0);
  return (
    <main>
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>Increment</button>
    </main>
  );
}

A <main><p>Count: 1</p><button>Increment</button></main>

B <main><p>Count: 0</p><button>Increment</button></main>

C <main><p>Count: NaN</p><button>Increment</button></main>

D <main><p>Count: -1</p><button>Increment</button></main>

💡 Hint

The button increases count by 1 on each click.

Initially count is 0. Clicking the button calls setCount(count + 1), so count becomes 1. The rendered text updates to 'Count: 1'.

❓ lifecycle

advanced

When does the useEffect run in this Next.js Page component?

Given this component, when will the console.log inside useEffect execute?

NextJS

import { useEffect } from 'react';

export default function Page() {
  useEffect(() => {
    console.log('Page mounted');
  }, []);
  return <main><h1>Hello</h1></main>;
}

A Every time the user clicks anywhere on the page.

B Every time the component re-renders.

C Only once after the component first renders on the client.

D Only on the server during initial render.

💡 Hint

An empty dependency array means the effect runs once after mount.

useEffect with an empty dependency array runs only once after the component mounts on the client side. It does not run on server or on re-renders.

🔧 Debug

expert

Why does this Next.js Page component cause a runtime error?

Examine this Page.tsx code. What causes the error when visiting this route?

NextJS

export default function Page() {
  const message = 'Hello';
  return (
    <main>
      <h1>{message.toUppercase()}</h1>
    </main>
  );
}

A The variable 'message' is not declared.

B The method 'toUppercase' is not defined on string, should be 'toUpperCase'.

C JSX elements must have a single parent element.

D The function is missing a return statement.

💡 Hint

Check the spelling of string methods used inside JSX.

JavaScript strings have a method 'toUpperCase' with a capital 'C'. Using 'toUppercase' causes a runtime TypeError because it's undefined.

Practice

1. In Next.js App Router, what does a Page.tsx file represent?

easy

A. A route that renders the default exported React component

B. A configuration file for server settings

C. A CSS stylesheet for styling components

D. A utility file for API calls

Solution

1. Step 1: Understand the role of Page.tsx in Next.js App Router

   A Page.tsx file automatically defines a route based on its folder location.

2. Step 2: Identify what the file exports

   The default export of Page.tsx is the React component rendered when visiting that route.

3. Final Answer:

   A route that renders the default exported React component -> Option A

4. Quick Check:

   Page.tsx = route component [OK]

Hint: Page.tsx file = route + component [OK]

Common Mistakes:

• Thinking Page.tsx is for styling or config
• Confusing Page.tsx with API route files
• Assuming Page.tsx exports multiple components

2. Which of the following is the correct way to define a route component in Page.tsx?

easy

A. export default function Page() { return Hello }

B. function Page() { return Hello }

C. export function Page() { return Hello }

D. const Page = () => { Hello }

Solution

1. Step 1: Check for default export

   Next.js requires the route component to be the default export from Page.tsx.

2. Step 2: Verify the function returns JSX correctly

   The function must return JSX explicitly; arrow functions need a return statement or parentheses.

3. Final Answer:

   export default function Page() { return <div>Hello</div> } -> Option A

4. Quick Check:

   Default export + returns JSX = export default function Page() { return
   Hello } [OK]

Hint: Default export function returning JSX is correct [OK]

Common Mistakes:

• Missing default export
• Arrow function without return statement
• Named export instead of default

3. Given this folder structure in Next.js App Router:
/app/about/Page.tsx exports a component showing <h1>About Us</h1>.
What will be rendered when visiting /about in the browser?

medium

A. An error because Page.tsx is missing

B. About Us

C. A blank page

D. The content of the root Page.tsx

Solution

1. Step 1: Map folder to route

   The folder /app/about corresponds to the route /about.

2. Step 2: Render the default export from Page.tsx

   The Page.tsx inside /about exports a component rendering <h1>About Us</h1>.

3. Final Answer:

   <h1>About Us</h1> -> Option B

4. Quick Check:

   Folder name = route, Page.tsx renders component [OK]

Hint: Folder name = route URL, Page.tsx renders content [OK]

Common Mistakes:

• Confusing root Page.tsx with nested routes
• Expecting error if Page.tsx exists
• Thinking route needs explicit config

4. What is wrong with this Page.tsx file?

export default function Page() {
  
Welcome

}

medium

A. Function name must be lowercase

B. Page.tsx cannot export a function

C. JSX must be wrapped in a fragment

D. Missing return statement inside the function

Solution

1. Step 1: Check function body for return

   The function body has JSX but no return keyword, so it returns undefined.

2. Step 2: Understand JSX rendering requirement

   React components must return JSX explicitly or implicitly; missing return causes no render.

3. Final Answer:

   Missing return statement inside the function -> Option D

4. Quick Check:

   JSX without return = error [OK]

Hint: Always return JSX from component functions [OK]

Common Mistakes:

• Assuming JSX auto-returns without return
• Thinking function name case matters
• Believing JSX must be wrapped in fragment always

5. You want to create a nested route /dashboard/settings in Next.js App Router. Which folder and file structure correctly defines this route?

hard

A. /app/dashboard-settings/Page.tsx

B. /app/dashboard/Page.tsx and /app/settings/Page.tsx

C. /app/dashboard/settings/Page.tsx with default export component

D. /app/dashboard/settings.tsx

Solution

1. Step 1: Understand nested route folder structure

   Nested routes are created by nesting folders inside /app matching the URL path segments.

2. Step 2: Identify correct file placement

   The route /dashboard/settings requires /app/dashboard/settings/Page.tsx with a default export component.

3. Final Answer:

   /app/dashboard/settings/Page.tsx with default export component -> Option C

4. Quick Check:

   Nested folders + Page.tsx = nested route [OK]

Hint: Nested folders match nested routes, Page.tsx inside last folder [OK]

Common Mistakes:

• Placing Page.tsx in wrong folder
• Using dash instead of nested folders
• Naming file settings.tsx instead of Page.tsx