Deno is a simple, modern, and secure runtime for JavaScript and TypeScript that uses V8 and is built in Rust programming language.
Topics Covered
Getting Started with Deno – Intro
In simple words, deno is a secure runtime environment for both javascript and typescript. It is built on top of V8, Rust, and TypeScript and developed by Ryan Dahl.
V8 is an open-source JavaScript engine developed by The Chromium Project for Google Chrome and Chromium web browsers.
Rust is a multi-paradigm programming language focused on performance and safety, especially safe concurrency.
Deno Highlights
| Initial release | 13 May 2018 |
| Stable release | 1.2.0 / July 13, 2020 |
| Preview release | 1.0.0-rc3 / May 12, 2020 |
| Original author | Ryan Dahl |
| Operating system | Linux, macOS, Windows |
| Written in | TypeScript, JavaScript, Rust, C++ |
Deno Features
The features provided by deno as per the official website are:
- Deno is secure by default, we need to explicitly provide access.
- Supports typescript out of the box.
- Works well with standard modules.
- Has built-in utilities like deno info and deno fmt.
- It ships only a single executable file.
Installing DenoJS
Installing deno JS is quite a simple process. Deno ships as a single executable with no dependencies.
There are two ways for installing deno js.
- Using Binaries
- Using Commands
Using Binaries
You can download a release binary from the official deno releases page.
Using Commands
Shell (Mac, Linux):
$ curl -fsSL https://deno.land/x/install/install.sh | sh
PowerShell (Windows):
$ iwr https://deno.land/x/install/install.ps1 -useb | iex
For the complete set of commands, please refer 👉 https://deno.land
First Deno JS program
Now, since we have successfully installed deno, let us run our first piece of code using deno js.
The file welcome.ts is a typescript file with a simple console message “Welcome to Deno 🦕” and is hosted on deno land website.
We will directly run that file from our PowerShell command prompt.
$ deno run https://deno.land/std/examples/welcome.ts
Installing Deno and Running the first program:
DenoJS using VSCode
Now, let’s write a bit complex code using one of our favorite code editor – VS Code. In case if you don’t have VS Code installed on your machine, get it from code.visualstudio.com, it’s free 🙂
Let’s open the VS Code, create a file named “hello.js” and paste the given code(taken from deno.land).
import { serve } from "https://deno.land/std@0.63.0/http/server.ts";
const s = serve({ port: 8000 });
console.log("http://localhost:8000/");
for await (const req of s) {
req.respond({ body: "Hello World\n" });
}
Now, running this code we would expect “Hello World” as output into the browser window.
[Solved] Uncaught PermissionDenied Error
While running our program using,
deno run hello.js
We got this error:
Uncaught PermissionDenied: network access to “0.0.0.0:8000”, run again with the –allow-read flag
Why this error while running our first piece of code?
Deno is secure by default. Therefore, unless we specifically enable it, a deno module has no excess to file, network, or environment. So, we need to grant permission explicitly.
–allow-net – For accessing the net
–allow-read – For reading files
–allow-write – For writing files
For our code, in order to solve this error, we need to pass the additional flag “–allow-net” along with deno run command.
deno run --allow-net hello.js
This will run our program and ask us to navigate to http://localhost:8000/ using the Ctrl + Click.
Summary
Let’s summarize all our learning with respect to getting started with deno js.
- Deno is not a replacement for node js.
- Deno is a secure runtime for both JavaScript and TypeScript.
- If you’re using typescript extensively then using deno.js you may get rid of your extra javascript compilers like babel.
- Deno does not use npm nor does package.json.
If you are stuck somewhere, please refer to the deno manual for more information.
Getting Started With Deno – Courses
These two courses look good to me for deno.js concepts.
1️⃣ Deno: The Complete Guide Zero to Mastery
2️⃣ Mastering Deno.js: Beginner to Expert [2020]
Getting Started With Deno – Youtube
This video explains the basics of deno.js in 5 minutes and helps you in Getting Started With Deno. You may check it out and subscribe to the channel.
Deno Tutorial
If you are looking for step by step tutorial on denojs, then you may refer to our tutorial space.
👉 Deno Tutorial – Getting Started With Deno
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