Why Deno uses URL-based imports - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import a module from a URL in Deno.

Deno

import { serve } from "[1]";

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

Ahttp/server

B./server.ts

Chttps://deno.land/std/http/server.ts

Ddeno_std/http

Attempts:

3 left

💡 Hint

Common Mistakes

Using relative paths instead of full URLs.

Omitting the file extension in the URL.

Deno imports modules directly from URLs, so the import path must be a full URL.

2fill in blank

medium

Complete the code to fetch and run a remote module in Deno.

Deno

const response = await fetch("[1]");

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

Ahttps://example.com/module.ts

B/module.ts

Chttp://localhost/module.ts

Dmodule.ts

Attempts:

3 left

💡 Hint

Common Mistakes

Using relative or local paths instead of full URLs.

Using http instead of https for secure fetching.

Deno fetches modules from full URLs, so the URL must be complete and accessible over the internet.

3fill in blank

hard

Fix the error in the import statement by completing the URL correctly.

Deno

import { parse } from "[1]";

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

Adeno.land/std/flags/parse

Bhttps://deno.land/std/flags/parse.ts

C./flags/parse.ts

Dflags/parse

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting https:// in the URL.

Leaving out the .ts file extension.

The import must be a full URL including the protocol and file extension for Deno to load it correctly.

4fill in blank

hard

Fill both blanks to create a URL-based import and use it in Deno.

Deno

import { serve } from "[1]";

serve(() => new Response("Hello from [2]!"));

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

Ahttps://deno.land/std/http/server.ts

Bhttps://deno.land/std/http/server.js

Chttps://deno.land/std/http/server

Dhttp://deno.land/std/http/server.ts

Attempts:

3 left

💡 Hint

Common Mistakes

Using http instead of https.

Omitting the .ts extension in the URL.

Use the correct full URL with https and .ts extension for importing, and the same name can be used in the response message.

5fill in blank

hard

Fill all three blanks to create a URL import, call a function, and handle the response in Deno.

Deno

import { [1] } from "[2]";

const response = [3]();
console.log(await response.text());

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

Aserve

Bhttps://deno.land/std/http/server.ts

Cserve()

Dfetch

Attempts:

3 left

💡 Hint

Common Mistakes

Using fetch instead of serve for the function call.

Omitting the parentheses when calling serve.

Import the serve function from the correct URL, then call serve() to start the server and handle the response.

Practice

1. Why does Deno use URL-based imports instead of traditional package managers?

easy

A. To allow direct loading of code from the web without extra tools

B. Because URLs are faster than local files

C. To force users to always be online

D. Because it does not support local files

Solution

1. Step 1: Understand Deno's import system

   Deno imports modules directly using URLs, unlike Node.js which uses package managers like npm.

2. Step 2: Reason why URLs are used

   This design removes the need for separate package managers or local installs, simplifying dependency management.

3. Final Answer:

   To allow direct loading of code from the web without extra tools -> Option A

4. Quick Check:

   Direct web imports = To allow direct loading of code from the web without extra tools [OK]

Hint: Remember: Deno loads code directly from URLs, no package manager needed [OK]

Common Mistakes:

• Thinking URLs are slower than local files
• Believing Deno requires always online connection
• Assuming Deno cannot use local files

2. Which of the following is the correct syntax to import a module from a URL in Deno?

easy

A. require('https://deno.land/std/http/server.ts');

B. import { serve } from 'https://deno.land/std/http/server.ts';

C. import serve from 'http://localhost/server';

D. import * as serve from './server.ts';

Solution

1. Step 1: Identify correct import syntax in Deno

   Deno uses ES module syntax with import and URLs as module specifiers.

2. Step 2: Check each option

   import { serve } from 'https://deno.land/std/http/server.ts'; uses correct ES import with a full HTTPS URL. import serve from 'http://localhost/server'; uses HTTP but is less common and may be insecure. require('https://deno.land/std/http/server.ts'); uses Node.js style require, which Deno does not support. import * as serve from './server.ts'; imports local file, not URL.

3. Final Answer:

   import { serve } from 'https://deno.land/std/http/server.ts'; -> Option B

4. Quick Check:

   ES import + HTTPS URL = import { serve } from 'https://deno.land/std/http/server.ts'; [OK]

Hint: Look for ES import with full HTTPS URL syntax [OK]

Common Mistakes:

• Using Node.js require() instead of import
• Using local file path instead of URL
• Using HTTP instead of HTTPS

3. What will happen when you run this Deno code?

import { serve } from 'https://deno.land/std/http/server.ts';

serve(() => new Response('Hello from Deno!'), { port: 8000 });

medium

A. Runs but does not respond to HTTP requests

B. Throws a syntax error because of missing semicolons

C. Starts an HTTP server on port 8000 responding with 'Hello from Deno!'

D. Fails to run because local server.ts file is missing

Solution

1. Step 1: Understand the imported module and function

   The serve function from Deno's standard library starts an HTTP server.

2. Step 2: Analyze the code behavior

   The code starts a server on port 8000 that responds with 'Hello from Deno!' to any request.

3. Final Answer:

   Starts an HTTP server on port 8000 responding with 'Hello from Deno!' -> Option C

4. Quick Check:

   serve() starts server with response = Starts an HTTP server on port 8000 responding with 'Hello from Deno!' [OK]

Hint: Recognize serve() starts HTTP server with given response [OK]

Common Mistakes:

• Thinking semicolons are mandatory in Deno
• Assuming local files are needed for URL imports
• Believing server won't respond without extra setup

4. You wrote this import in Deno:

import { serve } from 'https://deno.land/std/http/server';

But it throws an error. What is the likely cause?

medium

A. The URL is missing the file extension '.ts'

B. Deno does not support HTTPS URLs

C. You must use require() instead of import

D. The server module does not export 'serve'

Solution

1. Step 1: Check URL correctness for Deno imports

   Deno requires full file paths including extensions like '.ts' in URLs.

2. Step 2: Identify error cause

   The import URL lacks '.ts' extension, causing Deno to fail resolving the module.

3. Final Answer:

   The URL is missing the file extension '.ts' -> Option A

4. Quick Check:

   Missing file extension in URL = The URL is missing the file extension '.ts' [OK]

Hint: Always include file extensions in Deno URL imports [OK]

Common Mistakes:

• Thinking HTTPS URLs are unsupported
• Using require() instead of import
• Assuming module exports are missing

5. You want to share a Deno script with a friend without using npm or other package managers. How does Deno's URL-based import system help you achieve this?

hard

A. You have to send your friend all local files to install

B. You must bundle all dependencies into one file manually

C. You need to publish your code to npm first

D. You can host your modules on a web server and import them via URLs directly

Solution

1. Step 1: Understand Deno's URL import advantage

   Deno allows importing modules directly from URLs, so code can be shared via web hosting.

2. Step 2: Apply this to sharing scripts

   By hosting your modules online, your friend can import them directly without installing packages or bundling.

3. Final Answer:

   You can host your modules on a web server and import them via URLs directly -> Option D

4. Quick Check:

   URL imports enable direct sharing = You can host your modules on a web server and import them via URLs directly [OK]

Hint: Host modules online to share via URL imports easily [OK]

Common Mistakes:

• Thinking you must bundle dependencies manually
• Assuming npm is required for sharing
• Believing local files must be sent physically