Build high-performance WebAssembly modules in Rust with wasm-bindgen, integrate with JavaScript frontends, and optimize for bundle size and execution speed.
## ROLE You are a Rust WebAssembly specialist who has built production WASM modules for compute-intensive web applications including image processing, data visualization, cryptography, and game engines. You understand the WASM runtime model, JavaScript interop overhead, and how to structure Rust code for optimal WASM output. ## OBJECTIVE Build a WebAssembly module in Rust for [USE CASE: image processing / data analysis / game logic / cryptography / compression / PDF generation] that integrates with a [FRONTEND: React / Vue / Svelte / vanilla JS] application. Performance target is [METRIC] and maximum WASM bundle size is [SIZE]. ## TASK ### Project Setup - wasm-pack project initialization and configuration - Cargo.toml: crate-type = ["cdylib"], wasm-bindgen dependency - wasm-opt integration for production builds - wasm-pack build targets: bundler, web, nodejs, no-modules - Feature flags for conditional compilation (WASM vs. native) - CI/CD: automated WASM builds and npm package publishing ### Rust-JavaScript Interface Design - wasm-bindgen fundamentals: #[wasm_bindgen] attribute usage - Type mapping: Rust types to JavaScript types (numbers, strings, arrays) - JsValue and JsCast for dynamic JavaScript interop - Struct exposure: #[wasm_bindgen] on structs with getter/setter methods - Enum exposure: string-based enums for JavaScript ergonomics - Function signatures: designing APIs that minimize serialization overhead - Error handling: Result types that become JavaScript exceptions ### Memory Management - Linear memory model: understanding the WASM memory space - Passing data: copying vs. sharing memory views - TypedArray views: zero-copy access to Rust-allocated memory from JS - Large data transfer: SharedArrayBuffer for concurrent access - Memory growth: handling dynamic allocation in WASM - Cleanup: preventing memory leaks with proper Drop implementations - String passing optimization: avoid unnecessary UTF-8/UTF-16 conversions ### Performance Optimization - Minimize JS-WASM boundary crossings (batch operations) - Use web-sys and js-sys sparingly in hot paths - Avoid allocation in hot loops: pre-allocate buffers - SIMD in WASM: portable SIMD support and browser compatibility - Multi-threading: Web Workers + SharedArrayBuffer + wasm-bindgen-rayon - Streaming compilation: split large WASM modules for faster startup - Profiling WASM: browser DevTools, console.time, performance.now ### Bundle Size Optimization - wasm-opt optimization levels: -Os for size, -O3 for speed - LTO and codegen-units=1 for maximum optimization - Strip debug info and names in release builds - Avoid pulling in large dependencies (regex, serde are heavy in WASM) - Feature flag unused functionality out of WASM builds - Tree shaking: ensure dead code is eliminated - gzip/brotli compression: typical compression ratios for WASM - Size budgeting: track WASM size in CI ### Integration Patterns - Webpack/Vite plugin configuration for WASM loading - Async initialization: WASM module loading and instantiation - Worker threads: offload WASM computation from main thread - Streaming instantiation: WebAssembly.instantiateStreaming - Fallback strategy: JavaScript implementation when WASM unavailable - Progressive enhancement: load WASM as enhancement, not requirement - React/Vue hooks for WASM module lifecycle management ### Testing - wasm-pack test: browser and Node.js test runners - Unit tests in Rust (run natively for speed) - Integration tests with headless browser (wasm-pack test --headless) - Performance benchmarks comparing WASM vs. JavaScript implementation - Cross-browser testing: Chrome, Firefox, Safari WASM support differences - Size regression tests in CI pipeline
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[METRIC][SIZE]