Hooks (handle, handleError, handleFetch) in Svelte - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What does the handle hook do in SvelteKit?

Consider the handle hook in SvelteKit. What is its main purpose?

A It intercepts every request and can modify the request or response before reaching the route handler.

B It only handles errors thrown during server-side rendering.

C It fetches data from external APIs automatically for all routes.

D It manages client-side navigation events and updates the URL.

💡 Hint

Think about a hook that runs for every request and can change how the server responds.

The handle hook runs on every request and allows you to modify the request or response, such as adding headers or handling authentication.

🔧 Debug

intermediate

What error does this handleError hook cause?

Given this handleError hook in SvelteKit:

export function handleError({ error, event }) {
  return { message: error.message };
}

What problem will this cause?

A It will cause the server to crash because <code>handleError</code> cannot access <code>event</code>.

B The error response will be missing the <code>stack</code> property, causing incomplete error info.

C It will cause a syntax error due to missing parentheses around the return object.

D It will cause a runtime error because <code>handleError</code> must return a string, not an object.

💡 Hint

Check what handleError expects to return for proper error display.

The handleError hook should return an object with message and optionally stack. Omitting stack means less debug info.

❓ state_output

advanced

What is the effect of this handleFetch hook on fetch requests?

Analyze this handleFetch hook:

export async function handleFetch({ request, fetch }) {
  if (request.url.includes('/api')) {
    const modifiedRequest = new Request(request, { headers: { 'X-Custom': 'true' } });
    return fetch(modifiedRequest);
  }
  return fetch(request);
}

What happens when the app fetches /api/data?

A The fetch request to <code>/api/data</code> includes the custom header <code>X-Custom: true</code>.

B The fetch request to <code>/api/data</code> is blocked and returns an error.

C The fetch request to <code>/api/data</code> is unchanged and has no extra headers.

D The fetch request to <code>/api/data</code> is redirected to another URL.

💡 Hint

Look at how the hook modifies requests with URLs containing /api.

The hook creates a new request with an added header X-Custom: true for URLs containing /api, so the fetch includes this header.

📝 Syntax

advanced

Which handle hook code snippet is syntactically correct?

Choose the valid handle hook implementation in SvelteKit:

A

export function handle({ event, resolve }) {
  const response = resolve(event);
  return response
}

B

export async function handle(event, resolve) {
  const response = await resolve(event);
  return response;
}

C

export async function handle({ event, resolve }) {
  const response = resolve(event);
  return response;
}

D

export async function handle({ event, resolve }) {
  const response = await resolve(event);
  return response;
}

💡 Hint

Check the function signature and usage of await.

The handle hook must be async if it awaits resolve. The function signature must destructure { event, resolve }.

🧠 Conceptual

expert

How do handle, handleError, and handleFetch hooks differ in SvelteKit?

Match each hook to its main responsibility in SvelteKit:

• handle
• handleError
• handleFetch

A <code>handle</code>: manages client-side state; <code>handleError</code>: retries failed fetches; <code>handleFetch</code>: modifies server responses.

B <code>handle</code>: only runs on client navigation; <code>handleError</code>: logs errors to console; <code>handleFetch</code>: caches fetch results.

C <code>handle</code>: modifies requests/responses globally; <code>handleError</code>: customizes error responses; <code>handleFetch</code>: intercepts and modifies fetch calls.

D <code>handle</code>: fetches data for routes; <code>handleError</code>: handles form submissions; <code>handleFetch</code>: manages cookies.

💡 Hint

Think about what each hook controls: requests, errors, or fetch calls.

handle runs on every request to modify requests or responses. handleError customizes error handling. handleFetch intercepts fetch calls to modify or monitor them.