wasm-bindings

name	wasm-bindings
description	wasm-bindgen conventions for compiling a Rust core to WebAssembly for JavaScript: wasm-pack packaging, JsValue mapping, async futures, bundle-size tuning, web-sys/js-sys, and TypeScript defs. Load when generating or reviewing WebAssembly/JS bindings for a Rust library.

• Use wasm-bindgen for JavaScript interop. Use wasm-pack for building and packaging.
• Map Rust types to JS with #[wasm_bindgen]. Use JsValue for dynamic types, typed wrappers for known types.
• Handle errors with Result<T, JsValue>. Convert Rust errors to descriptive JS error messages.
• Support both browser (ES modules) and Node.js (CommonJS/ESM) targets.
• Async: use wasm-bindgen-futures for Promise-returning functions. Never block the main thread.
• Bundle size: use opt-level = "z", lto = true, codegen-units = 1 in release profile.
• Use web-sys and js-sys for Web API access. Feature-gate platform-specific APIs.
• Test with wasm-pack test --headless --firefox and a JS test runner (e.g., Vitest or Jest) for JS integration tests.
• Generate TypeScript definitions automatically. Keep .d.ts files in sync with Rust exports.
• Anti-patterns: no std::thread (single-threaded), no synchronous I/O, no panics (becomes JS exception).