But what if it was?

What I would like to see is:

- a bytecode "language" that roughly corresponds to Javascript semantics, and that is what the engines interpret (and JIT compile)

- browsers still include a compiler to compile JS sourcecode to the bytecode. Possibly wasm could work, although it would need a lot more functionality, like native support for GC, and DOM access, etc.

- browsers include a disassmbler/decompiler to improve debugging the bytecode

Then simple sites, and development can use plain JS source, but for higher performance you can just deploy the pre-compiled bytecode.