Well V8 is the one that matters most. More users use Chrome then Firefox, so it's more important on the client-side. And server-side javascript is probably going to be running on V8. Node.js, Google's scripting platforms, all run V8.
It's like complaining if a C++ performance article only tested with GCC. Sure, there's other compilers out there, but that's the big one.
It's like complaining if a C++ performance article only tested with GCC. Sure, there's other compilers out there, but that's the big one.