Credit While I’m the author of this blog post, 99% of the work was done by Nicolas B. Pierron. So far, my role in this project has largely been to play the wise old advisor, nodding and smiling mischeviously whenever Nicolas started exploring new ideas, and emitting cryptic comments in Reverse Jedi Notation. A few months ago, we published a short (and mysterious) blog post in which we mentioned HolyJIT, an early research project towards a novel approach to writing JITs. In this blog post, I would like to detail a bit more the ideas behind HolyJIT.

In this entry, I’d like to discuss one of the most interesting and unusual aspects of the Binary AST: how we gain performance by turning proof-building into validation, and why this is very good news for performance (and maybe not so good news for file size).

“The key to making programs fast is to make them do practically nothing.” - Mike Haertel, creator of GNU Grep. Binary AST - “Binary Abstract Syntax Tree” - is Mozilla’s proposal for specifying a binary-encoded syntax for JS with the intent of allowing browsers and other JS-executing environments to parse and load code as much as 80% faster than standard minified JS. It has recently cleared Stage 1 of the TC39 standards process, and while the final byte-level format isn’t completely nailed down, we’re confident that the final implementation will deliver the impressive performance improvements promised by the prototype.

Hey, all cool kids have exciting Engineering Newsletters these days, so it’s high time the JavaScript Binary AST got one! Summary JavaScript Binary AST is a joint project between Mozilla and Facebook to rethink how JavaScript source code is stored/transmitted/parsed. We expect that this project will help visibly speed up the loading of large codebases of JS applications and will have a large impact on the JS development community, including both web developers, Node developers, add-on developers and ourselves.

In this blog post, I would like to introduce the JavaScript Binary AST, an ongoing project that we hope will help make webpages load faster, along with a number of other benefits. A little background Over the years, JavaScript has grown from one of the slowest scripting languages available to a high-performance powerhouse, fast enough that it can run desktop, server, mobile and even embedded applications, whether through web browsers or other environments.

A few weeks ago, Mozilla pulled the plug on its Connected Devices Experiment: a bunch of internal non-profit hardware-related startups. One of our main objectives was to determine if we could come up with designs that could help turn the tide against the spyware-riddled and gruyère-level security devices that are currently being offered (or pushed) to unwary users. One of the startups was Project Lighthouse. We tried to provide an affordable, simple and privacy-friendly tool for people suffering from vision impairment and who needed help in their daily life.

At its core, Lighthouse is an idea we have been discussing in Connected Devices: can we build a device that will help people with partial or total vision disabilities? From there, we started a number of experiments. I figured out it was time to braindump some of them. Our problem Consider the following example: How do we get from this beautiful picture of Mozilla’s Paris office to the text “PRIDE and PREJUDICE”, “Jane Austen”, “Great Books”, “Great Prices”, “$9.