This is my basic understanding... Consider the interpreters written to run JavaScript. They create ASTs in order to run it. WebAssembly should allow you to tar

This is my basic understanding... Consider the interpreters written to run JavaScript. They create ASTs in order to run it. WebAssembly should allow you to target the AST layer directly. The JS compatibility is a fallback. In order to have this fallback, the AST will be similar to that which is used for asm.js. Furthermore, whilst it's sensible to design WebAssembly with compatibility in mind at first, there's no reason why future versions of WebAssembly can't drop support for JS altogether (whether that'll happen or not remains to be seen). So long as WebAssembly v1 supports a JS fallback, then WebAssembly v2 (or whatever it's called) need not, so long as v1 is kept around. We're talking probably a decade away (if at all) but as far as I can see the end goal is a high-performance, language-neutral web, and JS fallback is just a stepping stone towards that goal. I'm sure JS will stick around on the web regardless.