Tracking issue for implemented methods on `JsTypedArray`

[jedel1043]

Implementation in https://github.com/boa-dev/boa/blob/main/boa_engine/src/object/builtins/jstypedarray.rs

• at
• get buffer
• get byteLength
• get byteOffset
• constructor
• copyWithin
• entries
• every
• fill
• filter
• find
• findIndex
• findLast
• findLastIndex
• forEach
• includes
• indexOf
• join
• keys
• lastIndexOf
• get length
• map
• reduce
• reduceRight
• reverse
• set
• slice
• some
• sort
• subarray
• toLocaleString
• toReversed
• toSorted
• toString
• values
• with
• @@iterator
• get @@toStringTag

Desired features

• Easily return the inner data as &[u8] or &Vec<u8>

[aryaveersr]

If I understand correctly, the methods need to call the respective method on TypedArray with a reference to the inner value and the arguments, do minor wrapping/unwrapping/conversions etc. and return as a JsValue right ?

[jedel1043]

If I understand correctly, the methods need to call the respective method on TypedArray with a reference to the inner value and the arguments, do minor wrapping/unwrapping/conversions etc. and return as a JsValue right ?

Yes, but some methods like toSorted haven't been implemented for TypedArray yet

[AngeloChecked]

Hi @jedel1043 and @aryaveersr
Are you actively addressing this issue? I am willing to assist if there are no concerns about potential overlap?

Just to get better the issue, are these implementations okay, or am I missing something?

/// Calls `TypedArray.prototype.keys()`.
pub fn keys(&self, context: &mut Context<'_>) -> JsResult<JsValue> {
    TypedArray::keys(&self.inner, &[], context)
}

/// Calls `TypedArray.prototype.entries()`.
pub fn entries(&self, context: &mut Context<'_>) -> JsResult<JsValue> {
    TypedArray::entries(&self.inner, &[], context)
}

/// Calls `TypedArray.prototype.findLast()`.
pub fn find_last(&self, predicate: JsFunction, context: &mut Context<'_>) -> JsResult<JsValue> {
    TypedArray::find_last(&self.inner, &[predicate.into()], context)
}

[jedel1043]

@AngeloChecked Yes, those implementations are good! It would be cool to see findLast return Option<JsValue>, but I don't think find does that, so we can leave that as a future improvement.

[jedel1043]

I'm not working on this at the moment; I'm a bit busy implementing other builtins.
@aryaveersr Are you working on any method from this issue?

[AngeloChecked]

Hi @jedel1043, Alright, I believe I can help with this now.

But i have a question for you: do you have for me any tips or guidelines for figuring out the type signatures of these functions?
From a less familiar perspective like mine, some of these can be a bit tricky. For example, could you confirm if my intuition is correct:

JsResult<Self> - (from sort, slice.. fn) Functions returning their own value, also with mutations.
JsResult<JsValue> - (from reduce.. fn) Used for very dynamic results
JsResult<Option<usize>> - (from index_of fn) Is Option used for handling potential undefined or -1 returns?

[jedel1043]

For example, could you confirm if my intuition is correct:

Yep, that's pretty much on point. Our rule is just to use the type system as strictly as we can when returning values, so if a method only returns an index, we return usize, or if the method always returns a string, we return JsString.

[AngeloChecked]

Hi @jedel1043, sorry for bombarding you with questions: I'm using boa_examples/jstypedarray.rs for testing new functions. I found the entries function returning an iterator, and I need to make step and value functions of iterables module public instead of pub(crate).

/// boa_engine/src/object/builtins/jstypedarray.rs
/// Calls `TypedArray.prototype.entries()`.
pub fn entries(&self, context: &mut Context<'_>) -> JsResult<JsValue> {
    BuiltinTypedArray::entries(&self.inner.clone().into(), &[], context)
}

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/entries

/// boa_examples/src/bin/jstypedarray.rs
let mut result = vec![];
let data: Vec<u8> = vec![1, 2, 3];
let array = JsUint8Array::from_iter(data, context)?;
let mut iterator = array.entries(context)?.get_iterator(context, None, None)?;
while !iterator.step(context)? {
    let item = iterator.value(context)?.as_object().unwrap().clone();
    let js_array = JsArray::from_object(item)?;
    let index = js_array.get(0, context)?.as_number().unwrap();
    let value = js_array.get(1, context)?.as_number().unwrap();
    result.push((index, value))
}
assert_eq!(vec![(0f64, 1f64), (1f64, 2f64), (2f64, 4f64)], result);

https://github.com/boa-dev/boa/blob/main/boa_examples/src/bin/jstypedarray.rs

///boa_engine/src/builtins/iterables/mod.rs
/// [spec]: https://tc39.es/ecma262/#sec-iteratorstep
pub fn step(&mut self, context: &mut Context<'_>) -> JsResult<bool> {
    self.step_with(None, context)
}

/// Gets the current value of the `IteratorRecord`.
pub fn value(&mut self, context: &mut Context<'_>) -> JsResult<JsValue> {
    self.set_done_on_err(|iter| iter.last_result.value(context))
}

https://github.com/boa-dev/boa/blob/main/boa_engine/src/builtins/iterable/mod.rs#L421
Commonly can I make api public like this? Or do you have any tips on testing iterators or a better approach?

[jedel1043]

@AngeloChecked I think you can skip iterator related methods for now. We haven't designed a good public API for Js iterators, so I'd prefer to wait until we have iterators done instead of rushing and exposing internal APIs that may as well change in the future.