fmu

A WASM library containing utilities for working with JavaScript modules. It's mostly useful for other libraries to be built upon, if a specific functionality is needed, with high performance.

How it works

es-module-lexer was the main inspiration for fmu. Instead of parsing JavaScript, it's enough to simply iterate over each characters to determine the code syntax. Skipping strings and comments are easy too as they have a predictable syntax and rules. When a correct sequence of characters is matched, along with backtracking, scope/depth tracking (for variable shadowing), that all passes. It provides enough heuristic for syntax analysis. This also means that compared to parsing, it may catch things incorrectly, but it's generally a tradeoff for performance.

What I've learned

This is my first project with Rust. The tooling was a breath of fresh air, along with WebAssembly being very simple to implement. The lower-level patterns, such as Rust's ownership concept, gets easier to work with once you understand the why (The book was of great help). The hardest part for me was dealing with futures since I used hyper and jumped straight to tokio, but over time it's fun language to code in.