Beyond Performance: 5 Years of Improving JavaScript on WebAssembly

Saúl Cabrera - Shopify

Running dynamic languages on Wasm is an undeniable reality and JavaScript is no exception. This talk explores the multidimensional problem of optimizing JavaScript on WebAssembly through the lens of 5 years of development of Javy(https://github.com/bytecodealliance/javy), one of the first JavaScript-on-Wasm toolchains to reach production use.

This talk hypothesizes that it’s possible to improve developer experience, toolchain extensibility, language feature support, code size, and also performance through simplicity as an optimization strategy: simpler runtime architectural choices open the door to unexpected a optimization opportunities and enable potential adoption of emerging WebAssembly proposals like GC and the JIT interface.

Aside from a walk through of how Javy has solved for the great majority of the dimensions mentioned above, this talk finalizes with a walk through of Javy’s new addition: an experimental ahead-of-time compiler, revealing what’s possible and what trade-offs need be made in order to ensure cohesion between performance and all the other critical dimensions.