| name | yo-wasm-integration |
| description | Build Yo libraries for WebAssembly and publish as npm packages. Use this when working with WASM targets, Emscripten, WASI, npm packaging, JavaScript/TypeScript wrappers, or browser/Node.js integration. |
| argument-hint | [WASM task, target, or integration question] |
Yo WASM Integration
Use this skill for compiling Yo projects to WebAssembly and packaging them for JavaScript/TypeScript consumption via npm.
When to use this skill
Use this skill when you need to:
- compile a Yo project to WebAssembly (Emscripten or WASI)
- set up an
npm/ package directory with JavaScript/TypeScript wrappers
- expose Yo functions to JavaScript via WASM memory and C ABI
- integrate a Yo WASM module into a Node.js or browser project
- debug WASM-specific compilation or runtime issues
- publish a Yo-backed npm package
Workflow
- Decide on target: Emscripten (browser + Node.js) or WASI (standalone/server).
- Define WASM build steps in
build.yo using build.executable with target: build.CompilationTarget.Wasm32_Emscripten and add_c_flags(...) for Emscripten settings.
- Create a JavaScript wrapper in
npm/ that loads the WASM module and exposes a clean API.
- Add TypeScript declarations (
index.d.ts) for type safety.
- Test the WASM module from both Node.js and browser contexts.
- Consult the WASM integration cheatsheet for patterns.
High-signal rules
- In
build.yo, use target: build.CompilationTarget.Wasm32_Emscripten for Emscripten WASM builds. Use step.add_c_flags(...) for Emscripten -s options.
- For single-file compilation, use
yo compile --cc emcc or yo compile --target wasm-wasi.
- WASM functions communicate through linear memory — pass pointers and lengths, not Yo types.
- JavaScript wrappers handle the string encoding/decoding boundary (
TextEncoder/TextDecoder).
- Use bitmask flags (powers of 2) to pass option sets through a single
i32 parameter.
- Yo's
str and String types are internal — export raw *(u8) + usize pairs for WASM APIs.
- Always test with
--sanitize address on native first, then verify WASM behavior matches.
- Emscripten exports are controlled by
-sEXPORTED_FUNCTIONS and -sEXPORTED_RUNTIME_METHODS.
- WASM modules can be loaded in Node.js using
WebAssembly.instantiate or Emscripten's generated JS glue.
- Errno values differ on WASM — use constants from
std/libc/errno, never hardcode numbers.
Resource
