Deno

1. What is Deno?

Deno is a new runtime for executing JavaScript and TypeScript outside of the web browser. It uses V8 and is built in Rust.

2. Why do I care?

Think Typescript but without Node's design flaws.

• Des not use npm. It uses modules referenced as URLs or file paths.
• Does not use package.json in its module resolution algorithm.
• All async actions return a promise.
• Requires explicit permissions for file, network, and environment access.
• Always dies on uncaught errors.
• Uses "ES Modules" and does not support require(). Third party modules are imported via URLs: import * as log from "https://deno.land/std/log/mod.ts";

3. Examples using Deno

Your first CLI

Open your laptop's terminal and type:

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

Your first Web Service

a. Write your web service code

Create new file called example.js

import { serve } from "https://deno.land/std@0.50.0/http/server.ts";
    for await (const req of serve({ port: 8000 })) {
    req.respond({ body: "Hello World\n" });
}

Notice that the import statement has a URL with a version number!

b. Run your web service

deno run --allow-net example.js

c. Open your browser at localhost:8000

=> Hello World

4. Install Deno

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

add to .bashrc:

export DENO_INSTALL="~/.deno"
export PATH="$DENO_INSTALL/bin:$PATH"

5. Links

• Deno 1.0 announcement