Environment variables ($env) in Svelte - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Svelte component using $env/static/private?

Consider this Svelte component that imports a private environment variable and displays it:

  <script>
    import { PRIVATE_API_KEY } from '$env/static/private';
  </script>

  <p>API Key: {PRIVATE_API_KEY}</p>

If the environment variable PRIVATE_API_KEY is set to abc123 at build time, what will the component render in the browser?

Svelte

<script>
  import { PRIVATE_API_KEY } from '$env/static/private';
</script>

<p>API Key: {PRIVATE_API_KEY}</p>

A API Key: undefined

B API Key: $env/static/private

C API Key: abc123

D API Key: null

💡 Hint

Remember that $env/static/private variables are replaced at build time.

The PRIVATE_API_KEY is statically injected during build, so the component renders the actual value abc123.

📝 Syntax

intermediate

Which import statement correctly accesses a public environment variable in SvelteKit?

You want to use a public environment variable named VITE_API_URL in your SvelteKit component. Which import statement is correct?

A import { VITE_API_URL } from '$env/dynamic/private';

B import { VITE_API_URL } from '$env/static/private';

C import { VITE_API_URL } from '$env/dynamic/public';

D import { VITE_API_URL } from '$env/static/public';

💡 Hint

Public variables start with VITE_ and are imported from $env/static/public.

Public environment variables prefixed with VITE_ are accessed via $env/static/public for static imports.

🔧 Debug

advanced

Why does this SvelteKit code throw an error at runtime?

Given this code snippet:

  <script>
    import { SECRET_KEY } from '$env/dynamic/private';
    console.log(SECRET_KEY);
  </script>

At runtime, the console shows undefined for SECRET_KEY. What is the most likely cause?

Svelte

import { SECRET_KEY } from '$env/dynamic/private';
console.log(SECRET_KEY);

A SECRET_KEY is not set in the environment at runtime.

B You must import from '$env/static/private' instead.

C SECRET_KEY must start with VITE_ to be accessible.

D You cannot use environment variables in SvelteKit.

💡 Hint

Dynamic private variables reflect the environment at runtime, not build time.

If SECRET_KEY is undefined at runtime, it means the environment variable is not set in the running environment. Dynamic imports read the actual environment variables when the app runs.

❓ state_output

advanced

What is the output of this Svelte component using $env/dynamic/public?

Consider this Svelte component:

  <script>
    import { env } from '$env/dynamic/public';
  </script>

  <p>API URL: {env.VITE_API_URL}</p>

If the environment variable VITE_API_URL is set to https://api.example.com at runtime, what will the component display?

Svelte

<script>
  import { env } from '$env/dynamic/public';
</script>

<p>API URL: {env.VITE_API_URL}</p>

A API URL: https://api.example.com

B API URL: undefined

C API URL: $env/dynamic/public

D API URL: null

💡 Hint

Dynamic public env variables reflect the environment at runtime.

The env object from $env/dynamic/public contains public variables available at runtime, so the component shows the actual URL.

🧠 Conceptual

expert

Which statement about SvelteKit environment variables is TRUE?

Choose the correct statement about environment variables in SvelteKit:

A Variables from '$env/static/public' are only available at runtime on the server.

B Variables imported from '$env/static/private' are replaced at build time and not exposed to client-side code.

C Dynamic environment variables can be imported using named imports from '$env/dynamic/private'.

D Public environment variables must start with 'PRIVATE_' to be accessible in client code.

💡 Hint

Think about build time vs runtime and public vs private variables.

Static private variables are replaced at build time and never exposed to client code. Public variables start with 'VITE_' and are accessible in client code. Dynamic env variables are accessed via the 'env' object, not named imports.

Practice

1. What is the main reason to use environment variables in a Svelte project?

easy

A. To avoid using any external libraries

B. To write all code inside a single file

C. To make the app run faster by skipping variables

D. To store settings outside the code for safety and flexibility

Solution

1. Step 1: Understand environment variables purpose

   Environment variables keep sensitive or changeable settings outside the main code, so you can change them without editing code.

2. Step 2: Connect to safety and flexibility

   This separation helps keep secrets safe and lets you adjust settings easily for different environments like development or production.

3. Final Answer:

   To store settings outside the code for safety and flexibility -> Option D

4. Quick Check:

   Environment variables = safety and flexibility [OK]

Hint: Environment variables keep secrets outside code [OK]

Common Mistakes:

• Thinking environment variables speed up the app
• Believing environment variables are for code organization only
• Confusing environment variables with libraries

2. Which import statement correctly accesses public environment variables in a Svelte component?

easy

A. import { PUBLIC_API_KEY } from '$env/static/public';

B. import { API_KEY } from '$env/static/private';

C. import { API_KEY } from '$env/dynamic/private';

D. import { PUBLIC_API_KEY } from '$env/dynamic/public';

Solution

1. Step 1: Identify public environment variable import

   Public variables are accessed from '$env/static/public' when known at build time.

2. Step 2: Match variable prefix and import path

   Public variables must start with 'PUBLIC_' and be imported from '$env/static/public' for static access.

3. Final Answer:

   import { PUBLIC_API_KEY } from '$env/static/public'; -> Option A

4. Quick Check:

   Public vars use static/public import [OK]

Hint: Public vars use $env/static/public import [OK]

Common Mistakes:

• Using private import paths for public variables
• Forgetting the PUBLIC_ prefix
• Mixing dynamic and static imports incorrectly

3. Given this Svelte code snippet, what will be displayed if the environment variable PUBLIC_APP_NAME is set to 'MyApp'?

import { PUBLIC_APP_NAME } from '$env/static/public';

<h1>Welcome to {PUBLIC_APP_NAME}!</h1>

medium

A. Welcome to MyApp!

B. Welcome to PUBLIC_APP_NAME!

C. Welcome to !

D. Error: Cannot find variable PUBLIC_APP_NAME

Solution

1. Step 1: Understand import of PUBLIC_APP_NAME

   The variable PUBLIC_APP_NAME is imported from '$env/static/public', so its value is available at build time.

2. Step 2: Check usage in template

   The variable is used inside the <h1> tag, so it will display the actual value 'MyApp'.

3. Final Answer:

   <h1>Welcome to MyApp!</h1> -> Option A

4. Quick Check:

   Static public env var shows actual value [OK]

Hint: Static public vars show real value in template [OK]

Common Mistakes:

• Expecting variable name instead of value
• Assuming variable is undefined without import
• Confusing static and dynamic imports

4. You try to access a private environment variable in a Svelte component using this code:

import { SECRET_KEY } from '$env/static/private';

console.log(SECRET_KEY);

But you get an error during build. What is the likely cause?

medium

A. SECRET_KEY must start with PUBLIC_ prefix

B. You must import from '$env/dynamic/public' instead

C. Private variables cannot be imported in client-side code

D. You forgot to declare SECRET_KEY in .env file

Solution

1. Step 1: Understand private env variable usage

   Private environment variables are only available on the server side and cannot be imported into client-side code.

2. Step 2: Recognize build error cause

   Importing private variables in a component that runs in the browser causes build errors because secrets must stay server-only.

3. Final Answer:

   Private variables cannot be imported in client-side code -> Option C

4. Quick Check:

   Private vars are server-only [OK]

Hint: Private vars only on server, not client [OK]

Common Mistakes:

• Adding PUBLIC_ prefix to private vars
• Using dynamic public import for private vars
• Assuming missing .env declaration causes build error

5. You want to show a greeting message in your Svelte app that changes based on a public environment variable PUBLIC_GREETING. You also want to update this message without rebuilding the app. Which approach should you use?

hard

A. Import PUBLIC_GREETING from $env/static/public and use it directly

B. Import PUBLIC_GREETING from $env/dynamic/public and use it in your component

C. Store PUBLIC_GREETING in a local variable inside the component

D. Hardcode the greeting message in the component

Solution

1. Step 1: Understand static vs dynamic public env variables

   Static public variables are fixed at build time, so changes require rebuilding the app.

2. Step 2: Use dynamic public env for runtime updates

   Dynamic public variables from '$env/dynamic/public' reflect environment changes without rebuilding, ideal for updating messages.

3. Final Answer:

   Import PUBLIC_GREETING from $env/dynamic/public and use it in your component -> Option B

4. Quick Check:

   Dynamic public env allows runtime updates [OK]

Hint: Use $env/dynamic/public for runtime env changes [OK]

Common Mistakes:

• Using static public import for dynamic needs
• Storing env vars in local variables without import
• Hardcoding messages instead of using env vars