Hi! We (pdubroy & marianoguerra) just launched an online book called WebAssembly from the Ground Up. It’s an online book to learn Wasm by building a simple compiler in JavaScript. This is the book we wish we’d had 3 years ago. Unlike many WebAssembly resources that focus on use cases and tooling, we wanted a deep dive into how Wasm actually works. We focus on the core of WebAssembly: the module format and the instruction set. We think the low-level details — the “virtual ISA” — are the most interesting part, and we had the crazy idea that writing a compiler is the best way to learn it. Over the course of the book, you’ll build up two things: 1: An “assembler library”, that can be used to produce WebAssembly modules. Here’s an example: <pre><code>const mod = module([ typesec([functype([], [])]), funcsec([typeidx(0)]), exportsec([export_(‘main’, exportdesc.func(0))]), codesec([code(func([], [instr.end]))]), ]); return Uint8Array.from(mod.flat(Infinity)); </code></pre> 2: A very simple compiler for a language called Wafer, which looks like this: <pre><code>extern func setPixel(x, y, r, g, b, a);

func draw(width, height, t) { let y = 0; while y < height { let x = 0; while x < width { let r = t; let g = x; let b = y; let a = 255; setPixel(x, y, r, g, b, a); x := x + 1; } y := y + 1; } 0 } </code></pre> In case you’re not a fan of JavaScript, we’ve already heard of readers who’ve worked through the book in F# and Haskell. :-D You can check out a sample here: <a href=“https://wasmgroundup.com/book/contents-sample/” rel=“ugc”>https://wasmgroundup.com/book/contents-sample/</a> — we’d love to hear what you think! There’s also a 25% discount for Lobsters readers — just use the code LOBSTERS25 at checkout.