Hi HN!<p>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.<p>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.<p>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.<p>Over the course of the book, you'll build up two things:<p>1. An "assembler library", that can be used to produce WebAssembly modules. Here's an example:<p><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:<p><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<p>You can check out a sample here: <a href="https://wasmgroundup.com/book/contents-sample/" rel="nofollow">https://wasmgroundup.com/book/contents-sample/</a> — we'd love to hear what you think! There's also a 25% discount for HN readers — just use the code HNWASM25 at checkout.