Key Takeaways

• Deno is a JavaScript runtime built with security in mind.
• Deno provides many helper functions to streamline frequent operations.
• Deno supports non-transpiled TypeScript
• Deno strives to address some challenges with Node.js
• It’s incredibly easy to create web servers and manage files with Deno

What is Deno?

Deno is a simple, modern, and secure runtime for JavaScript and TypeScript applications built with the Chromium V8 JavaScript engine and Rust, created to avoid several pain points and regrets with Node.js.

Deno was originally announced in 2018 and reached 1.0 in 2020, created by the original Node.js founder Ryan Dahl and other mindful contributors.

Get Deno

The easiest way to install Deno is to use the deno_install scripts. You can do this on Linux or macOS with:

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

Windows users can leverage Chocolatey:

choco install deno

A successful install with  Linux looks like this:

Note: You may also need to export the deno directories to make the deno command globally available.

There are additional ways to install Deno.

Hands-on Deno

Simple Example

Deno uses .js and .ts file extensions (though it will run any JavaScript or TypeScript file regardless of extension). Our first example demonstrates how we can safely write a browser-based Deno application, a simple JavaScript program that prints the current date and time.

// date_time.js

console.log(new Date());

Let’s run the code:

deno run date_time.js

Results:

2020-07-10T02:20:31.298Z

Example 2: Accessing the Command-line Arguments

With Deno, we can log command-line arguments with just one line of code:

// first_argument.js

console.log(Deno.args[0]);

Running Deno Programs

The run command runs any Deno code. And if you’re stuck, run deno --help, or deno -h, to get help using denocommands.

Deno also provides a way to run programs from a local file, a URL, or by integrating with other applications in the stdin by using "-" (without quotes).

Running code from filename:

deno run date_time.js

Running code from a URL is nearly identical:

deno run https://example.com/date_time.js

Read code from stdin:

echo "console.log('Hello Deno')" | deno run 

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