Error handling with error.tsx in NextJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the error.tsx file in Next.js?

The error.tsx file is used to create a custom error page that handles unexpected errors in your Next.js app, showing friendly messages instead of default error screens.

beginner

How do you trigger an error to be caught by error.tsx in Next.js?

You can throw an error inside your components or server functions. Next.js will catch it and render the error.tsx page automatically.

intermediate

Which React hook is commonly used inside error.tsx to log error details?

The useEffect hook is often used to log or handle side effects when an error occurs, but Next.js passes error info as props to error.tsx for display.

beginner

What is a good user experience practice when designing an error page in error.tsx?

Show a clear message explaining something went wrong, provide a way to go back or reload, and keep the design consistent with the rest of your app.

intermediate

Can error.tsx handle both client-side and server-side errors in Next.js?

Yes, error.tsx handles errors from both client and server, providing a unified way to show error messages across your app.

What file name does Next.js use by default for custom error pages?

A app-error.tsx

B 404.tsx

C custom-error.tsx

D error.tsx

Next.js uses error.tsx as the default file for custom error pages.

How does Next.js know to show your custom error page?

A When you call a special Next.js API

B When you import <code>error.tsx</code> manually

C When an error is thrown in your app

D When you refresh the page

Next.js automatically shows the custom error page when an error is thrown anywhere in your app.

Which of these is NOT a good practice for error pages?

A Display raw error stack to users

B Show a friendly message

C Provide navigation options

D Keep design consistent with app

Showing raw error stacks can confuse users and expose sensitive info; better to show friendly messages.

Can error.tsx receive error details as props?

A Yes, Next.js passes error info as props

B No, it only shows static content

C Only if you use a special hook

D Only on client side

Next.js passes error details as props to error.tsx so you can display or log them.

What happens if you don't create an error.tsx file?

A App crashes without message

B Next.js shows a default error page

C Errors are ignored

D App reloads automatically

Without error.tsx, Next.js shows its default error page.

Explain how Next.js uses error.tsx to handle errors in your app.

Think about what happens when your app crashes.

Describe best practices for designing a user-friendly error page in error.tsx.

Imagine you are helping a friend who sees an error.

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