[jessaustin]

Speed is entirely separate from the language. It's possible to write two different JS interpreters: one very fast and one very slow, both of which meet the language standard set by ECMA.

If so, you're basically agreeing with parent, in parent's disagreement with this from further upthread:

JS semantics are garbage... for optimizations

[tps5]

Yeah, in retrospect I responded without thinking.

Of course the semantics of a language can impact how easy/hard it is to write a fast implementation for that language. And as far as I know, there isn't anything special about the ECMA specification that makes it any harder to speed up compared to other languages in the same space (dynamic languages, whose specifications were written with an interpreter approach in mind).

Still, in my mind, speeding up any sufficiently dynamic languages with eval and metaprogramming without straying at all from the language spec is like "fitting a square peg inside a round hole." And I think that has been done successfully with JS, at the cost of making it harder to reason about how the compiler is going to treat my code.

[Dylan16807]

Most code isn't using eval. It's okay if that part is slow. But even the most basic operations in javascript have all sorts of weird hooks that slow down evaluation. Most of it is little to no benefit to the programmer while a huge pain to the implementation.