Error handling with error.tsx in NextJS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What will the error.tsx component render when an error occurs?

Consider a Next.js app with an error.tsx file exporting a default error component. What will the user see if a runtime error happens in a page?

NextJS

export default function Error() {
  return <h1>Something went wrong!</h1>;
}

A The page shows the default Next.js error overlay with stack trace

B The page shows a blank screen with no content

C The page reloads automatically without showing any message

D The page shows a heading: 'Something went wrong!'

💡 Hint

The error.tsx component is used to display UI when an error happens in the app.

The error.tsx file exports a React component that Next.js renders when an error occurs. It replaces the default error overlay with the custom UI you provide.

📝 Syntax

intermediate

Which option correctly defines an error.tsx component that accepts an error prop?

You want to show the error message inside your error.tsx component. Which code is correct?

A

export default function Error({ error }: { error: Error }) {
  return <p>{error.message}</p>;
}

B

export default function Error(error) {
  return <p>{error.message}</p>;
}

C

export default function Error(props: Error) {
  return <p>{props.message}</p>;
}

D

export default function Error({ error }) {
  return <p>{error}</p>;
}

💡 Hint

Remember to type the props object correctly in TypeScript.

Option A correctly destructures the error prop and types it as an Error object. This allows accessing error.message safely.

❓ state_output

advanced

What happens if you throw an error inside a server component in Next.js 14 with error.tsx present?

Given a server component that throws an error during rendering, and an error.tsx file exists, what will the user see?

NextJS

export default function ServerComponent() {
  throw new Error('Failed to load data');
}

A The error is logged but the page renders normally without error UI

B The error.tsx component UI is rendered showing the error message

C The app crashes and shows a blank page with no UI

D Next.js shows a full error overlay with stack trace in production

💡 Hint

Next.js uses error.tsx to catch errors in server components and show fallback UI.

When a server component throws an error, Next.js renders the error.tsx component to show a user-friendly error UI instead of crashing.

🔧 Debug

advanced

Why does this error.tsx component fail to display the error message?

Look at this error.tsx code. Why does it not show the error message when an error occurs?

NextJS

export default function Error() {
  return <p>{error.message}</p>;
}

A The error object is not passed as a prop or defined, so error is undefined

B The component must be a class component to access error

C The error.message is not a valid property and causes a runtime error

D The component should return a fragment <> instead of a <p> tag

💡 Hint

Check if the error variable is defined or passed in the component.

The component tries to access error.message but error is not defined or passed as a prop, causing a ReferenceError.

🧠 Conceptual

expert

How does Next.js decide when to render error.tsx versus not showing it?

In Next.js 14, under what conditions will the error.tsx component be rendered automatically?

A Only when the developer manually imports and renders error.tsx

B Only when a client component throws an error during user interaction

C When a rendering error occurs in a server or client component inside the app directory

D When a page is not found (404 error) but not for runtime errors

💡 Hint

Think about automatic error boundaries in Next.js app router.

Next.js automatically renders error.tsx when any rendering error happens in the app directory components, both server and client side.

Practice

1. What is the main purpose of the error.tsx file in a Next.js route?

easy

A. To catch and display errors that happen in that route

B. To define the page layout and styles

C. To fetch data from an API

D. To handle user authentication

Solution

1. Step 1: Understand the role of error.tsx

   This file is designed to catch errors that occur in its route and show a friendly message to users.

2. Step 2: Compare with other options

   Options A, C, and D describe unrelated tasks like layout, data fetching, or authentication, which are not the purpose of error.tsx.

3. Final Answer:

   To catch and display errors that happen in that route -> Option A

4. Quick Check:

   Error handling = To catch and display errors that happen in that route [OK]

Hint: Remember: error.tsx shows errors in its route [OK]

Common Mistakes:

• Confusing error.tsx with layout.tsx
• Thinking error.tsx fetches data
• Assuming error.tsx manages authentication

2. Which of the following is the correct way to export an error component in error.tsx for Next.js?

easy

A. const Error = () => { Error occurred }; export default Error;

B. function Error() { return Error occurred; }

C. export default function Error() { return Error occurred; }

D. export function Error() { return Error occurred; }

Solution

1. Step 1: Check correct export syntax

   Next.js expects a default export for the error component in error.tsx. export default function Error() { return

   Error occurred

   ; } uses export default function, which is correct.

2. Step 2: Identify syntax errors in other options

   function Error() { return

   Error occurred

   ; } lacks export, so it won't be recognized. export function Error() { return

   Error occurred

   ; } exports a named function, not default. const Error = () => {

   Error occurred

   }; export default Error; misses a return statement inside the arrow function, causing no output.

3. Final Answer:

   export default function Error() { return <p>Error occurred</p>; } -> Option C

4. Quick Check:

   Default export function = export default function Error() { return

   Error occurred

   ; } [OK]

Hint: Use default export function for error component [OK]

Common Mistakes:

• Forgetting to export default
• Using named exports instead of default
• Missing return statement in arrow function

3. Given this error.tsx component, what will be rendered when an error occurs?

export default function Error() {
  return (
    <section role="alert">
      <h1>Oops! Something went wrong.</h1>
      <button onClick={() => window.location.reload()}>Try again</button>
    </section>
  );
}

medium

A. An error message but no button

B. A blank page with no content

C. A console error but no UI change

D. A section with a heading and a button that reloads the page

Solution

1. Step 1: Analyze the JSX structure

   The component returns a <section> with role="alert", containing a heading and a button with an onClick that reloads the page.

2. Step 2: Understand the rendered output

   When an error happens, this UI shows a message and a clickable button that refreshes the page, matching A section with a heading and a button that reloads the page.

3. Final Answer:

   A section with a heading and a button that reloads the page -> Option D

4. Quick Check:

   JSX returns alert section with reload button = A section with a heading and a button that reloads the page [OK]

Hint: Look for JSX elements and event handlers to predict output [OK]

Common Mistakes:

• Ignoring the button's onClick behavior
• Assuming no UI renders on error
• Confusing role attribute with content

4. You wrote this error.tsx but it does not show the error UI when an error happens:

function Error() {
  return <p>Error!</p>;
}
export default Error;

What is the likely problem?

medium

A. The component name must be lowercase

B. The file must be named error.tsx and placed in the route folder

C. The component is not exported as default

D. The component must return a div, not a p

Solution

1. Step 1: Check export and component name

   The component is exported as default and named with uppercase, which is correct.

2. Step 2: Verify file placement and naming

   Next.js requires the error.tsx file to be in the route folder to catch errors there. If misplaced or misnamed, it won't work.

3. Final Answer:

   The file must be named <code>error.tsx</code> and placed in the route folder -> Option B

4. Quick Check:

   Correct file name and location = The file must be named error.tsx and placed in the route folder [OK]

Hint: Check file name and folder location for error.tsx [OK]

Common Mistakes:

• Using lowercase component name
• Returning wrong HTML tags
• Not placing error.tsx in the route folder

5. You want to improve accessibility in your error.tsx component. Which change best helps screen reader users?

hard

A. Add role="alert" to the container element

B. Use only <div> elements without roles

C. Remove all buttons to avoid confusion

D. Use inline styles to highlight the error text

Solution

1. Step 1: Understand accessibility roles

   Adding role="alert" tells screen readers to announce the error immediately, improving accessibility.

2. Step 2: Evaluate other options

   Use only <div> elements without roles lacks roles, reducing accessibility. Remove all buttons to avoid confusion removes helpful retry buttons. Use inline styles to highlight the error text styles visually but doesn't help screen readers.

3. Final Answer:

   Add <code>role="alert"</code> to the container element -> Option A

4. Quick Check:

   Use ARIA roles for accessibility = Add role="alert" to the container element [OK]

Hint: Use ARIA roles like role="alert" for error messages [OK]

Common Mistakes:

• Ignoring ARIA roles for screen readers
• Removing interactive elements unnecessarily
• Relying only on visual styles for errors