I'm also doubtful that this will beat C, however...
> There is innate overhead when using an interpreted language, no matter how advanced the interpreter.
There is an overhead in JIT'ing the code, yes. But it is not a given that when amortised over sufficient data, that this overhead can not be compensated for by making use of knowledge that is simply not there at compile time. E.g. there are several well known methods regularly used in optimising dynamic languages that depend on discovering and adapting the code based on the actual types used. But when you're first doing this specialisation at runtime, nothing would stop you from taking actual input data into account rather than just basic type information for example.
> JavaScript is also garbage collected, while C is not, adding an additional level of overhead.
This is not necessarily a benefit for C unless a) your JavaScript program uses enough memory to trigger the garbage collector, which will depend on both the VM and your system, or b) your C program is written in a way that requires no extra effort to keep track of when memory becomes garbage. Programs written for GC'd systems may sometimes require far less logic to keep track of memory, and instead take the cost at collection time, and so may spend less time dealing with memory in situations where collection isn't necessary during the lifetime of the program.
In the general case, there's an extra overhead. In specific cases it is most certainly possible that the garbage collection can be a performance benefit by acting like a safety net that lets you do other stuff (avoiding logic to track ownership) that can speed up your app - this applies regardless of language.
> There is innate overhead when using an interpreted language, no matter how advanced the interpreter.
There is an overhead in JIT'ing the code, yes. But it is not a given that when amortised over sufficient data, that this overhead can not be compensated for by making use of knowledge that is simply not there at compile time. E.g. there are several well known methods regularly used in optimising dynamic languages that depend on discovering and adapting the code based on the actual types used. But when you're first doing this specialisation at runtime, nothing would stop you from taking actual input data into account rather than just basic type information for example.
> JavaScript is also garbage collected, while C is not, adding an additional level of overhead.
This is not necessarily a benefit for C unless a) your JavaScript program uses enough memory to trigger the garbage collector, which will depend on both the VM and your system, or b) your C program is written in a way that requires no extra effort to keep track of when memory becomes garbage. Programs written for GC'd systems may sometimes require far less logic to keep track of memory, and instead take the cost at collection time, and so may spend less time dealing with memory in situations where collection isn't necessary during the lifetime of the program.
In the general case, there's an extra overhead. In specific cases it is most certainly possible that the garbage collection can be a performance benefit by acting like a safety net that lets you do other stuff (avoiding logic to track ownership) that can speed up your app - this applies regardless of language.
Other than that I agree with you.