Well, yes, but it comes with all the overhead of being a (partly) flawed language. Having a bytecode that allows, for instance, optional static and dynamic types would be much more direct than relying on type inference or separate native APIs (as are being introduced). Of course we have javascript now, so pragmatically languages should be compiled to it if we want them, but if there were to be an additional web bytecode, there would be many areas for improvement in terms of performance and safety.

JavaScript is a programming language that compiles to bytecode. It can be treated as object code, but it is a very different and higher-level thing than the term "bytecode" generally denotes.

Calling JavaScript "flexible bytecode" is like saying that all Turing-complete programming languages are the same, or that all objects capable of driving a nail into a piece of wood are equivalent. It's true in a very facile way. JavaScript can be treated kind of like bytecode, and all Turing-complete languages can be treated as a simulation of a Turing machine, but the details that these rough descriptions miss are more numerous and more significant than the details that actually went into forming the generalization.

JavaScript is a programming language that compiles to bytecode. It can be treated as object code, but it is very different and higher-level thing than the term "bytecode" generally denotes.