Why Deno was created to fix Node.js mistakes - Quick Recap

Recall & Review

beginner

What was one main reason Deno was created?

Deno was created to fix some design mistakes and security issues found in Node.js.

beginner

How does Deno improve security compared to Node.js?

Deno runs code in a secure sandbox by default and requires explicit permission to access files, network, or environment.

intermediate

Why does Deno use ES Modules instead of CommonJS like Node.js?

Deno uses ES Modules to follow modern JavaScript standards and improve compatibility with browsers.

intermediate

What is one way Deno simplifies dependency management compared to Node.js?

Deno uses URL imports directly without a package manager like npm, reducing complexity and central points of failure.

intermediate

How does Deno handle tooling differently than Node.js?

Deno includes built-in tools like a formatter, linter, and test runner, so developers don’t need to install many separate packages.

What security feature does Deno have that Node.js lacks by default?

A Runs code in a secure sandbox with permission controls

B Automatically updates all packages

C Uses CommonJS modules

D Requires a package.json file

Deno runs code in a secure sandbox and requires explicit permissions for file, network, or environment access.

Which module system does Deno use?

A CommonJS

B ES Modules

C AMD

D UMD

Deno uses ES Modules to align with modern JavaScript standards.

How does Deno handle dependencies?

A Requires manual download of packages

B Uses npm and package.json

C Bundles all dependencies into one file

D Imports modules directly via URLs

Deno imports modules directly from URLs, avoiding the need for a package manager like npm.

What built-in tools does Deno provide?

A No built-in tools

B Only a package manager

C Formatter, linter, and test runner

D Only a debugger

Deno includes built-in tools such as a code formatter, linter, and test runner.

Why was Deno created by the same person who made Node.js?

A To fix Node.js design mistakes and improve security

B To replace JavaScript with a new language

C To create a browser-based runtime

D To remove support for asynchronous code

Deno was created to fix design mistakes and security issues found in Node.js.

Explain why Deno was created to fix Node.js mistakes. What are the key improvements?

Think about security, modules, dependencies, and tools.

Describe how Deno’s approach to modules and dependencies differs from Node.js.

Focus on module system and how dependencies are loaded.

Practice

1. Why was Deno created as an improvement over Node.js?

easy

A. To make Node.js run faster without changes

B. To add support for older JavaScript versions

C. To fix security issues and simplify development

D. To remove TypeScript support completely

Solution

1. Step 1: Understand Node.js limitations

   Node.js had security risks and complex setup issues that developers faced.

2. Step 2: Identify Deno's goals

   Deno was designed to improve security and simplify the developer experience by default.

3. Final Answer:

   To fix security issues and simplify development -> Option C

4. Quick Check:

   Security and simplicity [OK]

Hint: Focus on security and simplicity as main goals [OK]

Common Mistakes:

• Thinking Deno removes TypeScript support
• Assuming Deno only speeds up Node.js
• Believing Deno targets older JavaScript versions

2. Which of the following is the correct way to run a TypeScript file in Deno?

easy

A. deno run myfile.ts

B. node myfile.ts

C. deno compile myfile.js

D. node run myfile.js

Solution

1. Step 1: Recall Deno's command for running scripts

   Deno runs TypeScript files directly using the command deno run filename.ts.

2. Step 2: Check other options

   Node.js cannot run TypeScript files without compilation. deno compile myfile.js is for compiling, not running.

3. Final Answer:

   deno run myfile.ts -> Option A

4. Quick Check:

   Deno runs TS files with 'deno run' [OK]

Hint: Remember: Deno runs TS files directly with 'deno run' [OK]

Common Mistakes:

• Using Node.js commands for TypeScript files
• Confusing compile and run commands
• Trying to run JavaScript files with Deno compile

3. What will be the output of this Deno script?

console.log(Deno.args.length);

when run with deno run script.ts one two?

medium

A. 0

B. undefined

C. 1

D. 2

Solution

1. Step 1: Understand Deno.args

   Deno.args is an array of command-line arguments passed after the script name.

2. Step 2: Count the arguments passed

   Running deno run script.ts one two passes two arguments: 'one' and 'two'.

3. Final Answer:

   2 -> Option D

4. Quick Check:

   Arguments count = 2 [OK]

Hint: Count arguments after script name in command line [OK]

Common Mistakes:

• Counting script name as argument
• Assuming no arguments passed
• Confusing Deno.args with process.argv

4. Identify the error in this Deno script:

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

serve(() => new Response("Hello"));

medium

A. serve function requires a port number argument

B. Missing permission flag to allow network access

C. Incorrect import URL for Deno standard library

D. Response constructor is not valid in Deno

Solution

1. Step 1: Check Deno's security model

   Deno requires explicit permission flags for network access when running scripts.

2. Step 2: Analyze the script's network usage

   The script uses serve to start a server, which needs network permission.

3. Final Answer:

   Missing permission flag to allow network access -> Option B

4. Quick Check:

   Network access needs permission flag [OK]

Hint: Remember to add --allow-net for network scripts [OK]

Common Mistakes:

• Assuming serve needs a port argument
• Thinking import URL is incorrect
• Believing Response is invalid in Deno

5. How does Deno improve security compared to Node.js when running scripts?

hard

A. By requiring explicit permission flags for file, network, and environment access

B. By disabling all network access permanently

C. By automatically sandboxing scripts without user control

D. By running scripts only in a browser environment

Solution

1. Step 1: Understand Node.js security model

   Node.js allows scripts to access files, network, and environment without restrictions by default.

2. Step 2: Identify Deno's security approach

   Deno requires users to explicitly grant permissions like --allow-net or --allow-read to scripts.

3. Final Answer:

   By requiring explicit permission flags for file, network, and environment access -> Option A

4. Quick Check:

   Explicit permission flags [OK]

Hint: Deno needs explicit permission flags for sensitive access [OK]

Common Mistakes:

• Thinking Deno disables network permanently
• Believing Deno auto-sandboxes without user input
• Assuming Deno runs scripts only in browsers