Why Deno Deploy enables edge computing - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the Deno Deploy runtime API.

Deno

import { [1] } from "https://deno.land/x/deploy/mod.ts";

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

Aserve

Bfetch

Clisten

Drun

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'fetch' instead of 'serve' to start the server.

Trying to import 'listen' which is not part of Deno Deploy API.

The 'serve' function is imported from Deno Deploy to handle HTTP requests at the edge.

2fill in blank

medium

Complete the code to respond with 'Hello from the edge!' to every request.

Deno

serve(() => new Response("[1]"));

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

AHello from the cloud!

BHello from Deno!

CHello from the edge!

DHello world!

Attempts:

3 left

💡 Hint

Common Mistakes

Using generic greetings that don't mention 'edge'.

Leaving the response empty.

The response text 'Hello from the edge!' shows the code runs at the edge.

3fill in blank

hard

Fix the error in the code to correctly handle the request event.

Deno

addEventListener("fetch", event => {
  event.[1](new Response("Edge computing!"));
});

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

ArespondWith

Brespond

Crequest

Dreply

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'request' instead of 'respondWith'.

Using 'reply' which is not a valid method.

The 'respondWith' method is used on the event to send the response asynchronously.

4fill in blank

hard

Fill both blanks to create a simple edge handler that returns JSON with a message and status.

Deno

serve(() => {
  const body = JSON.stringify({ message: "[1]" });
  return new Response(body, { status: [2] });
});

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

AHello from Deno Deploy

B200

C404

DEdge response

Attempts:

3 left

💡 Hint

Common Mistakes

Using status 404 which means not found.

Using a message unrelated to Deno Deploy.

The message is a greeting from Deno Deploy and status 200 means success.

5fill in blank

hard

Fill all three blanks to create a handler that reads a query parameter 'name' and responds with a personalized greeting or a default message.

Deno

serve(request => {
  const url = new URL(request.url);
  const name = url.searchParams.get("[1]") || "[2]";
  return new Response(`Hello, [3]!`);
});

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

Ausername

Bguest

C${name}

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'username' instead of 'name' as the query parameter.

Not using template string syntax for the greeting.

The query parameter is 'name', default is 'guest', and the greeting uses the variable 'name' inside a template string.

Practice

1. What is the main benefit of Deno Deploy running code near users in edge computing?

easy

A. It increases the size of the app's codebase.

B. It reduces the delay or latency for users accessing the app.

C. It requires users to install special software.

D. It makes the app run only on one central server.

Solution

1. Step 1: Understand edge computing basics

   Edge computing means running code close to users to reduce the time data travels.

2. Step 2: Connect Deno Deploy's role

   Deno Deploy runs code on many servers worldwide, so users get faster responses.

3. Final Answer:

   It reduces the delay or latency for users accessing the app. -> Option B

4. Quick Check:

   Edge computing = less delay = B [OK]

Hint: Edge computing means less delay by running code near users [OK]

Common Mistakes:

• Thinking edge computing increases app size
• Believing users need special software
• Assuming code runs only on one server

2. Which of the following is the correct way to deploy a simple Deno script to Deno Deploy?

easy

A. deno install main.ts

B. deno run main.ts

C. deno deploy --project=myapp main.ts

D. deno build main.ts

Solution

1. Step 1: Identify Deno Deploy command

   The command to deploy code to Deno Deploy is 'deno deploy' with project and file.

2. Step 2: Check other commands

   'deno run' runs locally, 'deno install' installs scripts, 'deno build' is not a Deno command.

3. Final Answer:

   deno deploy --project=myapp main.ts -> Option C

4. Quick Check:

   Deploy command starts with 'deno deploy' [OK]

Hint: Use 'deno deploy' to send code to Deno Deploy service [OK]

Common Mistakes:

• Using 'deno run' to deploy code
• Confusing install with deploy
• Trying 'deno build' which doesn't exist

3. Consider this Deno Deploy code snippet:

addEventListener('fetch', event => {
  event.respondWith(new Response('Hello from edge!'))
})

What will a user see when accessing this deployed script?

medium

A. The text 'Hello from edge!' displayed in the browser.

B. An error message about missing fetch handler.

C. A blank page with no content.

D. A JSON object with server details.

Solution

1. Step 1: Understand the fetch event listener

   The code listens for fetch requests and responds with 'Hello from edge!'.

2. Step 2: Determine the response content

   The response is a simple text string sent back to the user.

3. Final Answer:

   The text 'Hello from edge!' displayed in the browser. -> Option A

4. Quick Check:

   fetch event returns 'Hello from edge!' [OK]

Hint: fetch event responds with given text string [OK]

Common Mistakes:

• Expecting JSON instead of plain text
• Thinking no response is sent
• Confusing event listener with error

4. This Deno Deploy code throws an error when deployed:

addEventListener('fetch', event => {
  event.respondWith('Hello from edge!')
})

What is the error and how to fix it?

medium

A. Error: respondWith expects a Response object, fix by wrapping string in Response().

B. Error: fetch event missing, fix by adding fetch event listener.

C. Error: Syntax error, fix by adding semicolon after respondWith.

D. No error, code works fine as is.

Solution

1. Step 1: Identify respondWith argument type

   respondWith requires a Response object, not a plain string.

2. Step 2: Fix by wrapping string in Response()

   Use event.respondWith(new Response('Hello from edge!')) to fix error.

3. Final Answer:

   Error: respondWith expects a Response object, fix by wrapping string in Response(). -> Option A

4. Quick Check:

   respondWith needs Response object [OK]

Hint: respondWith must get Response object, not plain string [OK]

Common Mistakes:

• Passing string directly to respondWith
• Missing fetch event listener
• Assuming semicolon fixes error

5. You want to build a fast app using Deno Deploy that serves personalized greetings based on user location. Which feature of Deno Deploy best supports this edge computing use case?

hard

A. Requiring users to download the entire app before use.

B. Using global caching only without running code near users.

C. Running code on a single central server to simplify logic.

D. Running code on many servers worldwide close to users to reduce latency.

Solution

1. Step 1: Understand personalized greetings need low delay

   Personalized greetings require quick response based on user location.

2. Step 2: Identify Deno Deploy's edge computing feature

   Deno Deploy runs code on many servers worldwide near users to reduce delay.

3. Step 3: Compare options

   Only running code near users (Running code on many servers worldwide close to users to reduce latency.) supports fast personalized responses.

4. Final Answer:

   Running code on many servers worldwide close to users to reduce latency. -> Option D

5. Quick Check:

   Edge computing = code near users = A [OK]

Hint: Edge computing means code runs near users for speed [OK]

Common Mistakes:

• Thinking central server is faster
• Confusing caching with code execution
• Believing users must download app fully