Installing Deno

Introduction

Deno is a modern tool to run JavaScript and TypeScript outside the browser. Installing it lets you start building and running your code easily.

You want to run JavaScript or TypeScript programs on your computer without a browser.

You want a secure and simple environment to try new code quickly.

You need a tool that comes with built-in utilities like a code formatter and test runner.

You want to learn a modern alternative to Node.js for backend development.

Syntax

Deno

curl -fsSL https://deno.land/install.sh | sh

This command downloads and runs the official Deno installer script on Unix-like systems.

On Windows, you can use PowerShell with: iwr https://deno.land/install.ps1 -useb | iex

Examples

Run this in your terminal on macOS or Linux to install Deno.

Deno

curl -fsSL https://deno.land/install.sh | sh

Run this in PowerShell on Windows to install Deno.

Deno

iwr https://deno.land/install.ps1 -useb | iex

After installation, run this command to check if Deno is installed correctly and see its version.

Deno

deno --version

Sample Program

This command shows the installed Deno version and confirms the installation worked.

Deno

deno --version

Important Notes

Make sure you have internet access when running the installer.

After installation, add Deno to your system PATH if the installer does not do it automatically.

You can also install Deno using package managers like Homebrew on macOS: brew install deno

Summary

Deno is installed by running a simple script in your terminal or PowerShell.

Check installation by running deno --version.

Installation methods vary slightly by operating system.

Practice

1. What is the main command to check if Deno is installed correctly on your system?

easy

A. deno --version

B. deno install

C. deno start

D. deno run

Solution

1. Step 1: Understand the purpose of the command

   The command deno --version is used to check the installed version of Deno, confirming installation.

2. Step 2: Compare with other commands

   Other commands like deno install, deno start, and deno run are for running or installing scripts, not checking installation.

3. Final Answer:

   deno --version -> Option A

4. Quick Check:

   Check installation = deno --version [OK]

Hint: Use 'deno --version' to verify installation quickly [OK]

Common Mistakes:

• Trying to use 'deno install' to check installation
• Confusing 'deno run' with installation check
• Using 'deno start' which is not a valid command

2. Which of the following is the correct command to install Deno on Unix-like systems using the terminal?

easy

A. npm install -g deno

B. curl -fsSL https://deno.land/install.sh | sh

C. deno install https://deno.land/install.sh

D. wget https://deno.land/install.sh

Solution

1. Step 1: Identify the official installation method

   The official way to install Deno on Unix-like systems is to run the shell script via curl piped to sh.

2. Step 2: Evaluate other options

   npm install -g deno uses npm which is not used for Deno installation. deno install https://deno.land/install.sh is incorrect syntax. wget https://deno.land/install.sh downloads the script but does not execute it.

3. Final Answer:

   curl -fsSL https://deno.land/install.sh | sh -> Option B

4. Quick Check:

   Unix install = curl script | sh [OK]

Hint: Use curl with pipe to sh for Unix Deno install [OK]

Common Mistakes:

• Trying to install Deno with npm
• Downloading script without executing it
• Using incorrect command syntax

3. After running the installation script on Windows PowerShell, which command will show the installed Deno version if installation succeeded?

medium

A. deno --version

B. deno version

C. deno -v

D. deno check

Solution

1. Step 1: Recall the standard version check command

   The command deno --version is the official way to display the installed version.

2. Step 2: Understand why others are incorrect

   deno version and deno -v are not recognized commands. deno check checks code, not version.

3. Final Answer:

   deno --version -> Option A

4. Quick Check:

   Version command = deno --version [OK]

Hint: Use 'deno --version' to confirm installation on any OS [OK]

Common Mistakes:

• Using 'deno version' instead of 'deno --version'
• Trying 'deno -v' which is invalid
• Confusing 'deno check' with version command

4. You ran curl -fsSL https://deno.land/install.sh | sh on Linux but get a 'command not found' error for deno. What is the most likely cause?

medium

A. Deno is not supported on Linux

B. You need to restart your computer before using Deno

C. You must run the command as root user

D. The installation script did not add Deno to your PATH environment variable

Solution

1. Step 1: Understand the error meaning

   'command not found' means the shell cannot find the deno executable in the PATH.

2. Step 2: Identify common installation issue

   The script installs Deno but may not update PATH automatically, so the shell can't find it until PATH is updated.

3. Final Answer:

   The installation script did not add Deno to your PATH environment variable -> Option D

4. Quick Check:

   Command not found = PATH missing Deno [OK]

Hint: Check if Deno is in PATH after install to fix 'command not found' [OK]

Common Mistakes:

• Assuming a reboot is needed
• Thinking root user is required
• Believing Deno doesn't support Linux

5. You want to install Deno on macOS and ensure it is immediately available in your terminal. Which sequence of commands should you run?

hard

A. curl https://deno.land/install.sh | bash && reboot

B. brew install deno && source ~/.bash_profile

C. curl -fsSL https://deno.land/install.sh | sh && export PATH="$HOME/.deno/bin:$PATH"

D. npm install -g deno && deno --version

Solution

1. Step 1: Identify the official install method for macOS

   Running the curl script piped to sh installs Deno. Then updating PATH with export makes it available immediately.

2. Step 2: Evaluate other options

   brew install deno && source ~/.bash_profile uses Homebrew which is valid but requires shell reload; curl https://deno.land/install.sh | bash && reboot uses bash and reboot unnecessarily; npm install -g deno && deno --version uses npm which is incorrect for Deno.

3. Final Answer:

   curl -fsSL https://deno.land/install.sh | sh && export PATH="$HOME/.deno/bin:$PATH" -> Option C

4. Quick Check:

   Install + update PATH = curl -fsSL https://deno.land/install.sh | sh && export PATH="$HOME/.deno/bin:$PATH" [OK]

Hint: Install with curl script then export PATH to use Deno immediately [OK]

Common Mistakes:

• Using npm to install Deno
• Forgetting to update PATH after install
• Rebooting unnecessarily