Server load functions (+page.server.js) in Svelte - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to export a server load function in +page.server.js.

Svelte

export const load = async ([1]) => {
  return { message: 'Hello from server!' };
};

Drag options to blanks, or click blank then click option'

Arequest

Bevent

Cparams

Dcontext

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'request' instead of 'event' as the parameter name.

Leaving the parameter empty or missing.

The server load function receives an event object that contains request details.

2fill in blank

medium

Complete the code to access URL search parameters inside the server load function.

Svelte

export const load = async (event) => {
  const id = event.url.[1].get('id');
  return { id };
};

Drag options to blanks, or click blank then click option'

Aquery

Bparams

CsearchParams

Dsearch

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'params' which refers to route parameters, not query parameters.

Using 'query' or 'search' which are not valid properties on the URL object.

The url.searchParams property gives access to URL query parameters.

3fill in blank

hard

Fix the error in the server load function to correctly return data.

Svelte

export const load = async (event) => {
  const data = await fetch('/api/data');
  const json = await data.[1]();
  return { json };
};

Drag options to blanks, or click blank then click option'

Ajson

Bjsonify

CtoJSON

Dparse

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'jsonify' which is not a method on the Response object.

Using 'toJSON' which is for converting objects to JSON strings.

Using 'parse' which is not a method on the Response object.

The Response object has a json() method to parse JSON data.

4fill in blank

hard

Fill both blanks to destructure parameters and return a custom object in the server load function.

Svelte

export const load = async ([1]) => {
  const { params } = [2];
  return { id: params.id };
};

Drag options to blanks, or click blank then click option'

Aevent

Bcontext

Crequest

Durl

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for the parameter and destructured object.

Using 'context' or 'request' which are not the correct parameter names.

The event object contains params for route parameters.

5fill in blank

hard

Fill all three blanks to fetch data, parse JSON, and return it in the server load function.

Svelte

export const load = async ([1]) => {
  const response = await fetch('/api/items');
  const data = await response.[2]();
  return { [3] };
};

Drag options to blanks, or click blank then click option'

Aevent

Bjson

Citems

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong parameter names like 'request'.

Using incorrect methods like 'parse' instead of 'json'.

Returning a variable name that was not defined.

The parameter is event, the method to parse JSON is json(), and the returned object uses data.

Practice

1. What is the main purpose of a server load function in a +page.server.js file in SvelteKit?

easy

A. To fetch or prepare data on the server before the page loads

B. To handle client-side user interactions

C. To style the page components

D. To manage browser cookies on the client

Solution

1. Step 1: Understand server load function role

   Server load functions run on the server to get data before the page renders.

2. Step 2: Compare options to this role

   Only To fetch or prepare data on the server before the page loads describes fetching or preparing data on the server side before page load.

3. Final Answer:

   To fetch or prepare data on the server before the page loads -> Option A

4. Quick Check:

   Server load function = fetch data before page load [OK]

Hint: Server load functions run on server, not client [OK]

Common Mistakes:

• Confusing server load with client-side event handlers
• Thinking server load manages styles or cookies
• Assuming server load runs in the browser

2. Which of the following is the correct way to export a server load function in +page.server.js?

easy

A. export function load() { return { data: 'hello' }; }

B. export const load = () => { return { data: 'hello' }; }

C. export default function load() { return { data: 'hello' }; }

D. function load() { return { data: 'hello' }; }

Solution

1. Step 1: Recall SvelteKit server load export syntax

   Server load functions are exported as named exports, usually as a const arrow function.

2. Step 2: Check each option

   export const load = () => { return { data: 'hello' }; } uses export const load = () => { ... }, which is correct. export function load() { return { data: 'hello' }; } exports a function declaration but not as const, which is allowed but less common. export default function load() { return { data: 'hello' }; } uses default export which is incorrect. function load() { return { data: 'hello' }; } does not export at all.

3. Final Answer:

   export const load = () => { return { data: 'hello' }; } -> Option B

4. Quick Check:

   Named export const load = arrow function [OK]

Hint: Use named export const load = () => {} [OK]

Common Mistakes:

• Using default export instead of named export
• Not exporting the load function at all
• Using function declaration without export

3. Given this +page.server.js code, what will be the value of data.message in the page?

export const load = () => {
  return { message: 'Hello from server' };
};

medium

A. 'Hello from client'

B. undefined

C. An error occurs

D. 'Hello from server'

Solution

1. Step 1: Understand the load function return

   The load function returns an object with a property message set to 'Hello from server'.

2. Step 2: Recognize data passed to page

   The returned object properties become available as data in the page, so data.message equals 'Hello from server'.

3. Final Answer:

   'Hello from server' -> Option D

4. Quick Check:

   Returned object property = data property [OK]

Hint: Returned object keys become data properties [OK]

Common Mistakes:

• Expecting undefined if not wrapped in another object
• Confusing server message with client message
• Thinking load function causes error without async

4. What is wrong with this +page.server.js code?

export const load = async () => {
  const res = await fetch('/api/data');
  const data = await res.json();
  return data;
};

medium

A. The load function must not be async

B. Returning data directly instead of an object causes error

C. Fetching from '/api/data' on server causes an infinite loop

D. Missing export keyword

Solution

1. Step 1: Analyze fetch call in server load

   The load function fetches from '/api/data', which is likely a route handled by the same app.

2. Step 2: Understand server fetch behavior

   Fetching from an internal API route in server load can cause the server to call itself repeatedly, causing an infinite loop.

3. Final Answer:

   Fetching from '/api/data' on server causes an infinite loop -> Option C

4. Quick Check:

   Internal fetch in server load risks infinite loop [OK]

Hint: Avoid fetching internal routes directly in server load [OK]

Common Mistakes:

• Thinking async is not allowed in load
• Returning data directly is valid
• Forgetting to export load function

5. You want to load user data securely on the server and pass it to the page. Which approach correctly uses +page.server.js to fetch user info from a database and expose only the username?

hard

A. export const load = async () => {
const user = await db.getUser();
return { username: user.username };
};

B. export const load = async () => {
const user = await db.getUser();
return user;
};

C. export const load = () => {
fetch('/api/user').then(res => res.json());
return {};
};

D. export const load = async () => {
const user = await fetch('/api/user');
return { user };
};

Solution

1. Step 1: Identify secure data fetching on server

   export const load = async () => { const user = await db.getUser(); return { username: user.username }; }; fetches user data directly from the database on the server, which is secure.

2. Step 2: Check data exposure

   export const load = async () => { const user = await db.getUser(); return { username: user.username }; }; returns only the username property, exposing minimal info to the page.

3. Step 3: Evaluate other options

   export const load = async () => { const user = await db.getUser(); return user; }; returns full user object, exposing sensitive data. export const load = () => { fetch('/api/user').then(res => res.json()); return {}; }; uses client fetch incorrectly in server load. export const load = async () => { const user = await fetch('/api/user'); return { user }; }; fetches from API route which may cause loops or expose more data.

4. Final Answer:

   export const load = async () => { const user = await db.getUser(); return { username: user.username }; }; -> Option A

5. Quick Check:

   Server fetch minimal data, return only needed props [OK]

Hint: Fetch securely on server, return only needed data [OK]

Common Mistakes:

• Returning full user object exposing sensitive info
• Fetching from API route inside server load
• Using client fetch inside server load