V8 compiles code into bytecode and runs that. This is really simple.

V8 is a JIT compiler. It both compiles code and runs it. For your original complaint about not being able to compile JS up front, you're talking about Ahead-Of-Time (AOT) compilation. You don't seem very familiar with the relevant terminology.

In fact, I just looked it up and apparently V8 compiles JS directly to machine code rather than bytecode: https://en.wikipedia.org/wiki/Chrome_V8.