Deno

Ryan Dahl

2019.04.24

JS.LA

Disclaimer

This talk is aimed at experienced enthusiasts

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If this isn't you: Don't Panic

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Ignore this talk - use Node. Node isn't going anywhere!

Deno is a new command-line runtime

for executing JavaScript and TypeScript

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Primarily it is built on top of:

• V8
• Rust
• Tokio (event loop)
• TypeScript

But why!? Isn't this exactly what Node does?

JavaScript (both the language itself and the ecosystem around it) has changed significantly since Node was designed in 2009. Notably:

• Promises / Async / Await
• ES Modules
• Typed Arrays

Node has problems:

• A poorly designed module system, with centralized distribution.
• Lots of legacy APIs that must be supported.
• Security.

(These problems aren't unique to Node. Python and Ruby suffer similarly)

I want a fun and productive system for scripting.

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A good scripting platform is too useful of a tool to shrug and accept the status quo.

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I find neither Node nor Python nor Ruby nor any other dynamic language platform satisfactory.

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Deno attempts to correct design mistakes in Node by radically breaking compatibility

• ES modules are the one and only module system
• HTTP URLs are used to link to third party code
• Deno has the ability to fetch resources itself, so it is its own package manager.�
• Deno is secure by default
• Users must give extra permission to access the disk, network, or otherwise do privileged operations.�
• Deno maintains browser compatibility
• The subset of Deno programs which are written completely in JavaScript and do not use the global Deno object should also run in a modern web browser without change.

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V8 (C++)

Deno (Rust)

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deno::Isolate (Rust)

Uint8Array

Internal Design (VERY VERY simplified)

Deno.core.send()

Deno.core.recv()

JS

Demo 1

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deno help

REPL

Deno.metrics()

cat program

Deno is (kind of) like an OS

Linux

Processes

Syscalls

File descriptors (fd)

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Deno

Web Workers

Ops

Resource ids (rid)

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Demo 2

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location.href

import.meta

deno types

Demo 3

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http server

file_server

Embedding Deno

https://crates.io/crates/deno

Deno is released as a standalone executable, but it's also embeddable as a Rust crate.

Potential use cases:

• Databases often use a JavaScript for Map Reduce functions
• Serverless products like Lambda@Edge or Cloudflare Workers

Roadmap: Aiming for 1.0 by end of summer

Soon:

• I/O performance issues
• TLS (HTTPS)
• Lock file for external modules
• Hook into chrome debugger

Eventually:

• File system events
• WebGL

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Deno is an open collaboration of many people.

Contributions welcome!

And others!

Thanks!

Comments? Questions? Concerns?

ry@tinyclouds.org

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These slides: http://bit.ly/deno-jsla