Why Deno bundles development tools - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to run a Deno script with permissions.

Deno

deno run [1] script.ts

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

A--allow-net

B--help

C--version

D--unstable

Attempts:

3 left

💡 Hint

Common Mistakes

Using --help or --version flags which do not run scripts

Using --unstable without understanding permissions

The --allow-net flag grants network access, which is a common permission needed when running Deno scripts.

2fill in blank

medium

Complete the code to bundle a Deno script into a single file.

Deno

deno bundle [1] bundle.js

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

Abundle.js

Bmain.js

Cmod.ts

Dscript.ts

Attempts:

3 left

💡 Hint

Common Mistakes

Using the output file name as input

Using a JavaScript file when the source is TypeScript

The deno bundle command takes the source file as input, here script.ts, and outputs a bundled file.

3fill in blank

hard

Fix the error in the command to run a Deno script with all permissions.

Deno

deno run [1] script.ts

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

A--allow-all=true

B--allow-all

C--allow-all false

Attempts:

3 left

💡 Hint

Common Mistakes

Adding =true or false after the flag

Using spaces instead of no value

The correct flag to grant all permissions is --allow-all without any value or equals sign.

4fill in blank

hard

Fill both blanks to import and use the Deno standard library's path module.

Deno

import * as path from "[1]";
console.log(path.[2]("/foo", "bar"));

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

Ahttps://deno.land/std/path/mod.ts

Bhttps://deno.land/std/fs/mod.ts

Cjoin

Dresolve

Attempts:

3 left

💡 Hint

Common Mistakes

Importing from the fs module instead of path

Using resolve instead of join for combining paths

The path module is imported from the standard library URL, and join combines path segments.

5fill in blank

hard

Fill all three blanks to create a simple HTTP server using Deno's standard library.

Deno

import { serve } from "[1]";

const server = serve({ port: [2] });

for await (const req of server) {
  req.[3](200, { "content-type": "text/plain" }, new TextEncoder().encode("Hello Deno!"));
}

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

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

B8080

Crespond

Dlisten

Attempts:

3 left

💡 Hint

Common Mistakes

Using listen instead of respond to send response

Setting port to a string instead of a number

Importing from the wrong URL

The serve function is imported from the HTTP server module, the port is set to 8080, and respond sends the response.

Practice

1. Why does Deno include development tools like formatter, linter, and test runner by default?

easy

A. To require installing many separate packages manually

B. To make the runtime slower and more complex

C. To force developers to use only Deno-specific code

D. To help developers start projects quickly without extra setup

Solution

1. Step 1: Understand Deno's design goal

   Deno aims to simplify development by bundling tools so you don't need extra installs.

2. Step 2: Identify the benefit of bundled tools

   This helps developers start coding quickly and keeps tools consistent across projects.

3. Final Answer:

   To help developers start projects quickly without extra setup -> Option D

4. Quick Check:

   Bundled tools = faster setup [OK]

Hint: Bundled tools mean less setup hassle [OK]

Common Mistakes:

• Thinking Deno slows down by bundling tools
• Believing Deno forces special code
• Assuming manual installs are needed

2. Which command runs tests in Deno without installing extra tools?

easy

A. deno test

B. deno run test.js

C. deno install test

D. deno lint

Solution

1. Step 1: Recall Deno's built-in commands

   Deno includes a test runner accessible by the command deno test.

2. Step 2: Compare options

   deno run test.js runs a script but doesn't run tests specially; deno install test tries to install a tool which is unnecessary; deno lint checks code style, not tests.

3. Final Answer:

   deno test -> Option A

4. Quick Check:

   Run tests = deno test [OK]

Hint: Use 'deno test' to run tests directly [OK]

Common Mistakes:

• Using 'deno run' to run tests
• Trying to install test tools manually
• Confusing lint with test commands

3. What will happen if you run deno fmt on your code in a Deno project?

medium

A. It will show syntax errors without changing code

B. It will format your code automatically to a standard style

C. It will install formatting tools first

D. It will run your code as a script

Solution

1. Step 1: Understand the purpose of deno fmt

   This command formats code files automatically using Deno's built-in formatter.

2. Step 2: Eliminate other options

   It does not run code (that's deno run), nor does it install tools first because tools are bundled, and it does not just show errors without formatting.

3. Final Answer:

   It will format your code automatically to a standard style -> Option B

4. Quick Check:

   deno fmt = auto format code [OK]

Hint: deno fmt cleans code style fast [OK]

Common Mistakes:

• Thinking deno fmt runs code
• Assuming formatter needs install
• Confusing lint errors with formatting

4. You run deno lint but get an error saying command not found. What is the likely cause?

medium

A. Your code has syntax errors

B. You forgot to install the lint tool manually

C. You are using an old Deno version without bundled lint tool

D. You need to run deno fmt first

Solution

1. Step 1: Check Deno version and bundled tools

   Older Deno versions did not include linting by default, so the command may not exist.

2. Step 2: Understand that manual install is not needed in modern Deno

   Since Deno bundles tools now, manual install is unnecessary; syntax errors or formatting do not cause command not found errors.

3. Final Answer:

   You are using an old Deno version without bundled lint tool -> Option C

4. Quick Check:

   Old Deno lacks lint command [OK]

Hint: Check Deno version if lint command missing [OK]

Common Mistakes:

• Assuming manual install is always needed
• Blaming code errors for missing commands
• Thinking formatting fixes lint command

5. You want to ensure your Deno project code is consistent and error-free without installing extra tools. Which approach best uses Deno's bundled tools?

hard

A. Run deno fmt to format, deno lint to check style, and deno test to run tests

B. Install ESLint and Prettier manually, then run tests with deno run

C. Only run deno run since it checks everything automatically

D. Use third-party tools outside Deno for formatting and testing

Solution

1. Step 1: Identify Deno's bundled tools for code quality

   Deno includes deno fmt for formatting, deno lint for style checking, and deno test for running tests without extra installs.

2. Step 2: Compare with other options

   Installing external tools or relying only on deno run does not cover formatting or linting automatically; third-party tools add complexity.

3. Final Answer:

   Run deno fmt to format, deno lint to check style, and deno test to run tests -> Option A

4. Quick Check:

   Use bundled fmt, lint, test for quality [OK]

Hint: Use deno fmt, lint, test for full checks [OK]

Common Mistakes:

• Ignoring lint and format commands
• Installing unnecessary external tools
• Thinking deno run covers all checks