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When dealing with a managed language that has a JIT or AOT compiler it's often ideal to write lots of stuff in the managed language, because that enables inlini

When dealing with a managed language that has a JIT or AOT compiler it's often ideal to write lots of stuff in the managed language, because that enables inlining and other optimizations that aren't possible when calling into C. This is sometimes referred to as "self-hosting", and browsers do it a lot by moving things into privileged JavaScript that might normally have been written in C/C++. Surprisingly large amounts of the standard library end up being not written in native code.

internetter 2y ago
Oh, I am indeed surprised! I guess I always assumed that most of the JavaScript standard library was written in C++
- achierius 2y ago
  Well, most all of the compiler, runtime, allocator, garbage collector, object model, etc, are indeed written in C++ And so are many special operations (eg crypto functions, array sorts, walking the stack) But specifically with regards to library functions, like the other commentator said, losing out on in lining sucks, and crossing between JS and Native code can be pretty expensive, so even with things like sorting an array it can be better to do it in js to avoid the overhead... Eg esp in cases where you can provide a callback as your comparator, which is js, and thus you have to cross back into js for every element So it's a balancing game, and the various engines have gone back and forth on which functions are implemented in which language over time
- jitl 2y ago
  Much of the standard library in v8 is written in Torque, a custom language. https://v8.dev/docs/torque https://v8.dev/docs/torque Example file for array.find(…): https://github.com/v8/v8/blob/5fe0aa3bc79c0a9d3ad546b79211f07105f09585/src/builtins/array-find.tq#L120 https://github.com/v8/v8/blob/5fe0aa3bc79c0a9d3ad546b79211f0...
kenhwang 2y ago
Ruby has realized this as well. When running in YJIT mode, some standard library methods switch to using a pure ruby implementation instead of the C implementation because the YJIT-optimized-ruby is better performing.

internetter 2y ago

Oh, I am indeed surprised! I guess I always assumed that most of the JavaScript standard library was written in C++

achierius 2y ago
Well, most all of the compiler, runtime, allocator, garbage collector, object model, etc, are indeed written in C++ And so are many special operations (eg crypto functions, array sorts, walking the stack) But specifically with regards to library functions, like the other commentator said, losing out on in lining sucks, and crossing between JS and Native code can be pretty expensive, so even with things like sorting an array it can be better to do it in js to avoid the overhead... Eg esp in cases where you can provide a callback as your comparator, which is js, and thus you have to cross back into js for every element So it's a balancing game, and the various engines have gone back and forth on which functions are implemented in which language over time
jitl 2y ago
Much of the standard library in v8 is written in Torque, a custom language. https://v8.dev/docs/torque https://v8.dev/docs/torque Example file for array.find(…): https://github.com/v8/v8/blob/5fe0aa3bc79c0a9d3ad546b79211f07105f09585/src/builtins/array-find.tq#L120 https://github.com/v8/v8/blob/5fe0aa3bc79c0a9d3ad546b79211f0...

kenhwang 2y ago

Ruby has realized this as well. When running in YJIT mode, some standard library methods switch to using a pure ruby implementation instead of the C implementation because the YJIT-optimized-ruby is better performing.