Performance

Rust WASM is faster than JavaScript for CPU-bound tasks like image processing, cryptography, or complex math, but JavaScript wins for DOM manipulation and I/O due to lower overhead. Use WASM when you need raw computational power that JavaScript's interpreter cannot match.

cargo build --target wasm32-unknown-unknown --release
wasm-bindgen target/wasm32-unknown-unknown/release/my_lib.wasm --out-dir pkg

This compiles your Rust code to a WebAssembly binary optimized for performance, which you can then load into your web application.

Think of JavaScript as a translator who reads your instructions out loud, while Rust WASM is a native speaker who just does the work. You should use Rust WASM when you have heavy lifting to do, like crunching numbers or editing video, because it runs much closer to the hardware. For simple tasks like clicking buttons or fetching data, JavaScript is usually fast enough and easier to use.