Deno.js

What is Deno?

Deno is a JavaScript Runtime based on Chrome's V8 JavaScript Engine, which allows you to run JavaScript outside of the browser.

• Deno supports JavaScript and TypeScript
• Deno supports URL imports and modern JavaScript features (eg. Promises)
• Deno is "secure by default" and requires explicit execution permissions

Pros and Cons - Deno vs Node

Node

• CON: Only JavaScript, modern JS features are missing, custom module system, no script permissions
• PRO: Established, highly active ecosystem, used by thousands of (big) companies, huge base of maintainers, production-proven

Deno

• CON: Pretty new, small ecosystem, not used in production by major companies yet, smaller base of maintainers, not really used in production yet
• PRO: TypeScript support, modern JS features, URL imports, script permissions

Conclusion

If you don't need all the Deno enhancements, use Node

Basics

Homepage and Instructions: https://deno.land

Install with Homebrew (MacOS)

$ brew install deno

Check Install:

$ deno --version

Deno REPL

$ deno

Run a File

$ deno run <filename>

Re-fetch remote files with reload:

$ deno run --reload <filename>

VSCode Support

Download extension: Deno from denoland

You must enable Deno on a project level, so add a .vscode/settings.json to your main project directory enabling it:

{
    "deno.enable": true,
}

Permissions - Secure by Default

Give Deno permissions by adding flags.

For example, give Deno permission to write a file:

$ deno run --allow-write <filename>

For example, give Deno permission to write a specific file:

$ deno run --allow-write=<filename_to_write_to> <filename_to_run>

For example, give Deno permission to read a file:

$ deno run --allow-read <filename>

Deno Core, Standard Library and Third Party

Deno Namespace APIs

• stable and maintained by Core Team
• built-into Deno, no installation or imports required
• only a small set of low-level core functionalities
• Example: Deno.writeFile()
• https://doc.deno.land/builtin/stable

Standard Library

• unstable and maintained by Core Team
• needs to be imported into scripts to be used
• builds up on core, low-level functionalities to provide easier-to-use functionalities
• https://deno.land/std@0.77.0

3rd Party Libraries

• stability differs and maintained by community teams
• needs to be imported into scripts to be used
• builds up on core, low-level functionalities to provide easier-to-use functionalities
• https://deno.land/x

Deploy to Heroku

1. Create a Procfile with the following:

   web: deno run --allow-net --allow-write --allow-read --allow-plugin --allow-env --unstable --no-check app.ts
   

2. On the Heroku Dashboard, create a new application

3. On the new application, go to the Settings page

4. Click the Add buildpack button

5. Enter the following URL in the input box:

   https://github.com/chibat/heroku-buildpack-deno.git
   

6. Add your environment variables to under Settings -> Config Vars

7. Log in to heroku

   $ heroku login
   

8. Initialize Heroku git with your app

   $ heroku git:remote -a <your-app-name>
   

9. Commit your code

   $ git add .
   $ git commit -am 'commit message'
   $ git push heroku master
   

10. Logs for server

    $ heroku logs --tail