Usually, the native resizable array is good enough. But sometimes, you don't want to resize it, just allocate a slab of memory for objects. Typed arrays already implement this for integers, but I find it quite often in certain applications that I want to do this for arbitrary objects, too. So how about a `FixedArray` analogue to `TypedArray` that implements most the same stuff `TypedArray` does, just without the binary data integration or numeric coercion?
There's a few other benefits to having a native fixed-size untyped array: 1. Engines can make major assumptions about allocation and use that to improve performance and minimize allocations - notably, they can choose to allocate the array's entries in the object itself, since it can't change for the lifetime of that object. This is the norm in some languages, like Rust. 2. Engines can optimize things like `.map`, `.filter`, `.concat`, and similar far more easily. Those don't have to be generic, and since they can assume everything's contiguous, it's much easier to implement. 3. Engines can make guarantees about allocation size, and that's the whole point of this proposal. These objects only require a minimum of type info, GC info, its length, and `length` number of machine pointers. Of course, yes, normal arrays *could* provide most of these, but consider how V8 internally uses an `InternalArray` extensively to implement many JS built-ins in JS and its CodeStubAssembler DSL. It's also worth noting V8 didn't start inlining `Array.prototype.map` and friends for dense arrays until it figured out how to bail out of a JIT-compiled loop from within that loop with negligible overhead (it took an internal redesign), and no other engine I'm aware of performs this optimization, either - it's all because JS's resizable arrays can also be sparse. ----- Isiah Meadows cont...@isiahmeadows.com www.isiahmeadows.com _______________________________________________ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
