beta 3 parcel 2

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2021-05-20 15:34:40

The Parcel team is excited to release Parcel 2 beta 3! This release includes a ground up rewrite of our JavaScript compiler in Rust, which improves overall build performance by up to 10x. In addition, this post will cover some other improvements we’ve made to Parcel since our last update, along with our roadmap to a stable Parcel 2 release.

Over the past few months, we’ve been working on rewriting our JavaScript compiler in Rust! Parcel's JavaScript compiler is responsible for detecting dependencies in your code (like import statements and new Worker() calls), inlining process.env variables and other Node globals, and performing scope hoisting.

In addition, Parcel automatically transpiles your source code for your configured browserslist targets, along with non-standard syntax like JSX and TypeScript, and development features like React Fast Refresh.

Previously, all of this was implemented in JavaScript on top of a Babel AST. While we had made great progress optimizing this, JavaScript compilation was still by far the slowest part of Parcel. In particular, serializing large JavaScript ASTs to send between threads was very slow, and these large objects put a lot of pressure on the JavaScript garbage collector. Also, JavaScript code must be compiled by the engine every time it is run, which means it is slow to start up. While improving algorithmic complexity will result in performance improvements regardless of the language, that can only take you so far.