Developing a JavaScript engine in Rust can seem like pretty daunting task to some. In order to demystify working on a feature and to go over what we've been working on implementing in Boa recently, we thought we'd write a post about implementing a JavaScript feature in Rust.

More specifically, this will be the first in a series of posts primarily about implementing the new date/time built-in: Temporal. We'll be going over general lessons and interesting design choices we've stumbled upon, as well as the crates supporting that implementation.

Why should you care? Well, we are not only implementing Temporal for JavaScript, but for Rust as well ... more on that in a bit.

First, an aside!

What even is Temporal?​

Temporal is a modern API for handling date/time in a calendar and time zone aware manner that includes nine objects with over 200+ methods.

In this post, we will dive into how ECMAScript engines store variables, go over storage optimizations, and learn about scope analysis. If you are an ECMAScript developer, you will get some practical tips to improve the performance of your code. If you write your own ECMAScript engine or any interpreter/compiler, you might get some implementation ideas.

Summary​

Boa v0.20 is now available! After 5 months of development we are very happy to present you the latest release of the Boa JavaScript engine. Boa makes it easy to embed a JS engine in your projects, and you can even use it from WebAssembly. See the about page for more info.

In this release, our conformance has grown from 87.3% to 89.92% in the official ECMAScript Test Suite (Test262). This small jump is expected as we're shifting most of our focus to performance as the majority of the engine is now conformant. We will continue to implement more of the specification as we go along but we expect these changes to be much smaller than we've been used to.

You can check the full list of changes here, and the full information on conformance here.

Summary​

Boa v0.19 is now available! After 4 months of development we are very happy to present you the latest release of the Boa JavaScript engine. Boa makes it easy to embed a JS engine in your projects, and you can even use it from WebAssembly. See the about page for more info.

In this release, our conformance has grown from 85.03% to 87.3% in the official ECMAScript Test Suite (Test262). Interestingly, this was partly because around 2000 tests were removed from test262 as part of the removal of custom calendars and timezones. Overall, Boa's conformance in real terms has improved by ~6%.

You can check the full list of changes here, and the full information on conformance here.

Summary​

Boa v0.18 is now available! After 7 months of development we are very happy to present you the latest release of the Boa JavaScript engine. Boa makes it easy to embed a JS engine in your projects, and you can even use it from WebAssembly. See the about page for more info.

In this release, our conformance has grown from 79.36% to 85.03% in the official ECMAScript Test Suite (Test262). This means we now pass 3,550 more tests than in the previous version. Moreover, our amount of ignored tests decreased from 9,496 to 1,391 thanks to all the new builtins we have implemented for this release.

You can check the full list of changes here, and the full information on conformance here.

You probably noticed that something seems different... This release marks a major update to the design of our website, and the introduction of our new logo! We'd like to thank @ZackMitkin for being the one that started the work on this nifty redesign, and @kelbazz for designing the logo. We're planning to add some additional pages to learn more about the APIs that Boa exposes. Additionally, expect some more blog posts from us in the future! We would like to write about how to use certain APIs, design challenges that we encountered while developing the engine, and internal implementation details. Subscribe to our RSS feed if you're interested in staying up to date!

This big release was partly possible thanks to those who have supported us. Thanks to funds we've received we have been able to renew our domain name, remunerate members of the team who have worked on the features released, and discuss the possibility of using dedicated servers for benchmarking. If you wish to sponsor Boa, you can do so by donating to our open collective. You can also check easy or good first issues if you want to contribute some code instead.

Summary​

Boa v0.17 is now available! This is one of the biggest Boa releases since the project started, and after around 7 months of development, we are very happy to present you the latest release of the Boa JavaScript engine. Boa makes it easy to embed a JS engine in your projects, and you can even use it from WebAssembly. See the about page for more info.

In this release, our conformance has grown from 74.53% to 78.74% in the official ECMAScript Test Suite (Test262). While this might look as a small increase, we now pass 6,079 more tests than in the previous version. In any case, the big changes in this release are not related to conformance, but to huge internal enhancements and new APIs that you will be able to use.

You can check the full list of changes here, and the full information on conformance here.

Moreover, this big release was partly possible thanks to a grant by Lit Protocol. Thanks to this grant, we were able to remunerate 2 team members for their 20h/week work each during three and a half months. If you wish to sponsor Boa, you can do so by donating to our open collective. You can also check easy or good first issues.

Furthermore, we now have a new domain for Boa, boajs.dev.

Introduction​

When we develop tools for our users, we sometimes want to give them some form of control over how they work. This is common in games, where we can add scripting for our users to be able to create extensions, or even for business tools, where we allow our customer to change or extend the behaviour of our platform. For those cases, using Rust, a compiled, type safe language can be a challenge, since once a program has been compiled, it's tricky to change or extend it at runtime. Furthermore, many of our users will prefer to use a more common scripting language, such as JavaScript.

This is where Boa enters the scene. Boa is a Javascript engine fully written in Rust. Currently, it can be used in places where you need most of the JavaScript language to work, even though, we would advise to wait to get all our known blocker bugs solved before using this for critical workloads. You can check how conformant we are with the official ECMAScript specification here.

And, before going further, we would like to mention that you can contribute to Boa by solving one of the issues where we need special help, and we now also accept financial contributions in our OpenCollective page.

Note: You can see more examples of integrating Boa in our repository.

Summary​

Boa v0.16 is now available! After around 3 months of development, we are very happy to present you the newest release of the Boa JavaScript engine. Boa makes it easy to embed a JS engine in your projects, and you can even use it from WebAssembly. See the about page for more info.

Boa currently supports part of the JavaScript language. In this release, our conformance has grown from 62.29% to 74.53% in the official ECMAScript Test Suite (Test262). The engine now passes 68,612 tests, coming from 56,372 in Boa 0.15 (21.7% increase), and we have closed 9 issues and merged 59 pull requests. You can check the full list of changes here, and the full information on conformance here.

Summary​

Boa v0.15 is now available! After around 3 months of development, we are very happy to present you the newest release of the Boa JavaScript engine. Boa makes it easy to embed a JS engine in your projects, and you can even use it from WebAssembly. See the about page for more info.

Boa currently supports part of the JavaScript language. In this release, our conformance has grown from 49.74% to 62.29% in the official ECMAScript Test Suite (Test262). The engine now passes 56,372 tests, coming from 43,986 in Boa 0.14 (28.1% increase), and we have closed 18 issues and merged 58 pull requests. You can check the full list of changes here, and the full information on conformance here.

Summary​

Boa v0.14 is here! After almost 6 months of development, we are very happy to present you the newest release of the Boa JavaScript engine. Boa makes it easy to embed a JS engine in your projects, and you can even use it from webassembly. See the about page for more info. Together with this release, we present you: A new way to contribute to Boa, a virtual machine, usable examples and much more.

Boa currently supports part of the JavaScript language. In this release, our conformance has grown from 41.01% to 49.74% in the official ECMAScript Test Suite (Test262). The engine now passes 43,986 tests, coming from 33,192 in Boa 0.13 (32.5% increase), and we have closed 40 issues and merged 137 pull requests. You can check the full list of changes here, and the full information on conformance here.

Boa v0.13 is here! Boa is a JavaScript engine written in the Rust programming language. It makes it easy to embed a JS engine in your projects, and you can even use it from webassembly. See the about page for more info.

We currently support part of the language. In this release, our conformance has grown to 41.97% of the official ECMAScript Test Suite (Test262). We have closed 40 issues and merged 105 pull requests. You can check the full list of changes here.

This release brings some new features, such as support for calling Rust closures from JavaScript to improve better interopability between JS and Rust.

Boa v0.12 is here! Boa is a JavaScript parser, compiler and executor written in the Rust programming language. It makes it easy to embed a JS engine in your projects, and you can even use it from webassembly. See the About page for more info.

We currently support part of the language. In this release, our conformance has grown to 33.97% of the official ECMAScript Test Suite (Test262). In this release, we have closed 19 issues and merged 69 pull requests. You can check the full list of changes here.

Let's dive into the most relevant changes of this release.

Boa has reached a new release. v0.11, our biggest one yet!

Since v0.10 we've closed 77 issues and merged 129 pull requests. The engine has been faster and more compliant to the spec. Below are some of the highlights but please see the changelog for more information.

What is Boa? See the About page for more info.

Boa is an experimental Javascript lexer, parser and compiler written in Rust. It has support for some of the language, can be embedded in Rust projects fairly easily and also used from the command line. Boa also exists to serve as a Rust implementation of the EcmaScript specification, there will be areas where we can utilise Rust and its fantastic ecosystem to make a fast, concurrent and safe engine.

We have a long way to go, however v0.10 has been the biggest release to date, with 138 issues closed!

We have some highlights, but if you prefer to read the full changelog, you can do that here

Hello World!

Boa is an experimental Javascript lexer, parser and compiler written in Rust. It has support for some of the language, can be embedded in Rust projects fairly easily and also used from the command line.
Boa also exists to serve as a Rust implementation of the EcmaScript specification, there will be areas where we can utilise Rust and its fantastic ecosystem to make a fast, concurrent and safe engine.

Today we're pleased to announce our latest release, version 0.9.
v0.9 is by far the biggest release we've had since Boa began. You can find the full changes from the changelog. The milestone behind this version was further optimisation and an increase in new features. We can show you how we can identify areas that can be optimised.