What is Deno

Deno is a simple, modern and secure runtime for JavaScript and TypeScript that uses V8 and is built in Rust. - https://deno.land/

Install deno (MacOS, Linux)

More options are here

# [Caution] vscode deno plugin error may occur later
$ curl -fsSL https://deno.land/x/install/install.sh | sh

# Via brew (Recommended)
$ brew install deno

Simple example

From terminal

$ deno run https://deno.land/std/examples/welcome.ts
Welcome to Deno 🦕

File Server example

If you skip these options (--allow-net --allow-read), You will encounter an error.

# Wrong approach
$ deno run https://deno.land/std/http/file_server.ts
error: Uncaught PermissionDenied: read access to "/Users/seokjepark/Code/TIL", run again with the --allow-read flag

# Right approach
$ deno run --allow-net --allow-read https://deno.land/std/http/file_server.ts
HTTP server listening on http://0.0.0.0:4507/

Write File example

TextEncoder is an Wep API which generate a byte stream with UTF-8 encoding.

• WriteFile returns promise

• Await don't have to be in a Async function because Deno handles this.

// createFile.ts
const encoder = new TextEncoder();
const greetText = encoder.encode('Hello Deno\nWhere are you?');

await Deno.WriteFile('greet.txt', greeText);

Execute above with deno

$ deno run createFile.ts
error: Uncaught PermissionDenied: write access to "/Users/seokjepark/Code/deno-pg/greet.txt", run again with the --allow-write flag

$ deno run --allow-write createFile.ts
Hello Deno
Where are you?

Install

deno install {script} Install script as an executable.

$ deno install --allow-net --allow-read https://deno.land/std/http/file_server.ts
✅ Successfully installed file_server
/Users/seokjepark/.deno/bin/file_server

# To excecute:˜
$ file_server
HTTP server listening on http://0.0.0.0:4507/

Uninstall

$ rm `which deno`

VSCode Extensions

[Issue] When the exclamation point is displayed in the lower right deno icon, restart vscode.

https://github.com/denoland/vscode_deno

You can also find more examples from my repo: https://github.com/Parkseokje/deno-playground

Reference site

• Deno Official site

• Deno Crash Course

• Deno Deep Dive