Error.tsx for route errors in NextJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of an Error.tsx file in a Next.js route?

It provides a custom error UI that shows when a route encounters an error, helping users understand something went wrong instead of a blank or default error page.

intermediate

How do you define an error boundary component in Next.js using Error.tsx?

You export a React component named Error that receives an error prop and returns JSX to display the error message or UI.

intermediate

Which React hook is NOT used inside Error.tsx for route errors in Next.js?

Hooks like useState or useEffect are usually not necessary inside Error.tsx because it mainly displays static error info.

beginner

What props does the Error component receive in Next.js route error files?

It receives an error object prop containing details about the error that occurred during rendering or data fetching.

beginner

Why is it important to have a custom Error.tsx in your Next.js app?

It improves user experience by showing friendly messages and options instead of confusing default errors, and helps developers debug issues faster.

What does the Error.tsx file in a Next.js route primarily do?

A Displays a custom error message when a route fails

B Defines the main layout of the app

C Handles user authentication

D Fetches data for the route

The Error.tsx file is designed to show a custom error UI when a route encounters an error.

Which prop is passed to the Error component in Next.js error routes?

A params

B data

C error

D children

The Error component receives an error prop with details about the error.

What React feature does Next.js use to catch errors in route components?

A Context API

B Error boundaries

C Hooks

D Fragments

Next.js uses React error boundaries to catch errors and render Error.tsx.

Where should you place the Error.tsx file to handle errors for a specific route in Next.js App Router?

A In the <code>components</code> folder

B In the root <code>app</code> folder

C In the <code>public</code> folder

D Inside the route folder

Placing Error.tsx inside a route folder scopes error handling to that route.

What should you avoid doing inside Error.tsx for route errors?

A Fetching data asynchronously

B Displaying error messages

C Using props

D Returning JSX

Fetching data asynchronously is not recommended inside Error.tsx because it is for showing errors, not loading data.

Explain how to create a custom Error.tsx file for route errors in Next.js and what it should contain.

Think about how React error boundaries work and how Next.js uses this file.

Describe why having a custom error component improves user experience in a Next.js app.

Consider what happens if no custom error UI is provided.

Practice

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

easy

A. To define the main layout of the application

B. To display a friendly message when a route fails or an error occurs

C. To handle user authentication and login

D. To fetch data from an API for the route

Solution

1. Step 1: Understand the role of Error.tsx in Next.js

   Error.tsx is designed to catch errors in routes and show a user-friendly message instead of a broken page.

2. Step 2: Compare with other options

   Layouts, authentication, and data fetching are handled elsewhere, not in Error.tsx.

3. Final Answer:

   To display a friendly message when a route fails or an error occurs -> Option B

4. Quick Check:

   Error.tsx shows friendly error messages [OK]

Hint: Error.tsx shows errors, not layouts or data [OK]

Common Mistakes:

• Confusing Error.tsx with layout or data files
• Thinking Error.tsx handles authentication
• Assuming Error.tsx fetches API data

2. Which of the following is the correct way to export a default Error component in Error.tsx for Next.js?

easy

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

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

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

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

Solution

1. Step 1: Recall correct default export syntax in React/Next.js

   The correct syntax is to declare the function and export it as default in one statement.

2. Step 2: Identify syntax errors in other options

   function Error() { return
   Error occurred; } misses export, C exports a named function, D has invalid syntax.

3. Final Answer:

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

4. Quick Check:

   Default export uses 'export default function' [OK]

Hint: Default export needs 'export default function' [OK]

Common Mistakes:

• Forgetting to export the component
• Using named export instead of default
• Incorrect export syntax like 'default export'

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

export default function Error() {
  return (
    <main role="alert" aria-live="assertive">
      <h1>Oops! Something went wrong.</h1>
      <button onClick={() => window.location.reload()}>Try Again</button>
    </main>
  );
}

medium

A. A heading with an error message and a button to reload the page

B. A blank page with no content

C. Only a button that does nothing

D. An error stack trace displayed to the user

Solution

1. Step 1: Analyze the JSX returned by the Error component

   The component returns a main element with a heading and a button that reloads the page on click.

2. Step 2: Understand the button behavior

   The button triggers window.location.reload(), so it reloads the current page when clicked.

3. Final Answer:

   A heading with an error message and a button to reload the page -> Option A

4. Quick Check:

   Error component shows message + reload button [OK]

Hint: Look for JSX elements and button onClick behavior [OK]

Common Mistakes:

• Assuming no content renders
• Thinking button does nothing
• Expecting error stack trace to show

4. What is wrong with this Error.tsx component code?

export default function Error() {
  return (
    <div>
      <h1>Error!</h1>
      <button onClick={reloadPage}>Reload</button>
    </div>
  );
}

function reloadPage() {
  location.reload;
}

medium

A. The reloadPage function does not call location.reload() correctly

B. The button should not have an onClick handler

C. The component must use a <main> tag instead of <div>

D. The function reloadPage should be inside the component

Solution

1. Step 1: Check the reloadPage function implementation

   location.reload is a function and must be called with parentheses: location.reload()

2. Step 2: Verify other parts

   The button can have onClick, using div is allowed, and reloadPage can be outside the component.

3. Final Answer:

   The reloadPage function does not call location.reload() correctly -> Option A

4. Quick Check:

   Call functions with parentheses to execute [OK]

Hint: Check if functions are called with () [OK]

Common Mistakes:

• Forgetting parentheses on function calls
• Thinking onClick is invalid on button
• Believing HTML tags must be <main>

5. You want to improve accessibility in your Error.tsx component by adding ARIA roles and live regions. Which of these changes is best practice?

hard

A. Use a <div> with aria-hidden="true" around the error message

B. Remove all ARIA attributes to keep it simple

C. Add tabindex="-1" to the button only

D. Wrap the error message in a <main> with role="alert" and aria-live="assertive"

Solution

1. Step 1: Understand ARIA roles for error messages

   Using role="alert" and aria-live="assertive" notifies screen readers immediately about errors.

2. Step 2: Evaluate other options

   aria-hidden="true" hides content from screen readers, tabindex="-1" on button is unrelated, removing ARIA reduces accessibility.

3. Final Answer:

   Wrap the error message in a <main> with role="alert" and aria-live="assertive" -> Option D

4. Quick Check:

   Use role="alert" and aria-live for error accessibility [OK]

Hint: Use role="alert" and aria-live="assertive" for errors [OK]

Common Mistakes:

• Hiding error messages from screen readers
• Misusing tabindex on unrelated elements
• Removing ARIA attributes thinking they are optional