Does anyone have a good sense of the current performance impact of crossing the boundary between JS and WASM? I've often thought it'd be great to be able to expose high-performance data structures (and other infrastructure-level stuff) via WASM and then make use of them from JavaScript, but I seem to recall that the interop performance cost is currently too high to make it worth doing, which leaves WASM mainly only useful for long-running tasks, such as game engines, expensive graph layout algorithms and so forth.
> "The wasm-bindgen code generation has been designed with the future host bindings proposal in mind from day 1. As soon as that’s a feature available in WebAssembly, we’ll be able to directly invoke imported functions without any of wasm-bindgen‘s JS shims. Furthermore, this will allow JS engines to aggressively optimize WebAssembly manipulating the DOM as invocations are well-typed and no longer need the argument validation checks that calls from JS need. At that point wasm-bindgen will not only make it easy to work with richer types like strings, but it will also provide best-in-class DOM manipulation performance."
Edit: https://hacks.mozilla.org/2018/04/javascript-to-rust-and-bac...
> "The wasm-bindgen code generation has been designed with the future host bindings proposal in mind from day 1. As soon as that’s a feature available in WebAssembly, we’ll be able to directly invoke imported functions without any of wasm-bindgen‘s JS shims. Furthermore, this will allow JS engines to aggressively optimize WebAssembly manipulating the DOM as invocations are well-typed and no longer need the argument validation checks that calls from JS need. At that point wasm-bindgen will not only make it easy to work with richer types like strings, but it will also provide best-in-class DOM manipulation performance."