A Quick Look at Deno

Deno is a program that allows you to run JavaScript and TypeScript programs. Deno is a direct successor to Node.js and in fact Deno was written by the guy who wrote Node.js.

I started working on a small project that uses Deno so my first step was to install Deno and get a Hello World program up and running.

Installing Deno using the Choclately program.

Installing Deno was quick and easy. I use Windows and so I decided to use the Chocolatey installer system to install Deno. First I installed Chocolately. I opened a PowerShell shell with Administrator privileges and issued the command “Set-ExecutionPolicy AllSigned”. Then I installed Chocolatey with the hideous command:

Set-ExecutionPolicy Bypass -Scope Process -Force; [System.Net.ServicePointManager]::SecurityProtocol = [System.Net.ServicePointManager]::SecurityProtocol -bor 3072; iex ((New-Object System.Net.WebClient).DownloadString(‘https://chocolatey.org/install.ps1’))

Next, I opened a regular CMD shell with Administrator privileges. I installed Deno using the beautifully simple command:

choco install deno

Now I was ready to try a Hello World program for Deno. First I used JavaScript. I opened Notepad and created a file hello.js based on the Deno documentation example:

// hello.js
// Deno can run JavaScript

function capitalize(word) {
  return word.charAt(0).toUpperCase() + word.slice(1);
}

function hello(name) {
  return "Hello " + capitalize(name);
}

function main() {
  console.log(hello("adam"));
  console.log(hello("Barb"));
  console.log(hello("CARL"));
}

main()

I ran the program by typing the command

deno run hello.js

Nice. Simple.

Then I created a hello.ts TypeScript equivalent version of the program and ran it to prove that Deno can run TypeScript without having to manually transpile it to JavaScript. Very Nice!

// hello.ts
// Deno can run TypeScript directly

function capitalize(word: string): string {
  return word.charAt(0).toUpperCase() + word.slice(1);
}

function hello(name: string): string {
  return "Hello " + capitalize(name);
}

function main() {
  console.log(hello("doug"));
  console.log(hello("Evan"));
  console.log(hello("freD"));
}

main()

In my opinion, Deno is a big improvement over Node.js in many ways. I especially like Deno’s no-need-to-transpile TypeScript, integrated package manager (no need for NPM), direct use of ES6 modules, integrated security, and module handling. I hope Deno overcomes the massive head start that Node.js has. Computer science is continuously evolving and maybe Deno will be part of that evolution (or maybe not).

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Art is continuously evolving. Four illustrations by artist Mads Berg. His style is sort of an evolved form of 1920s art deco.