I notice that operations accepting positive integers do various somewhat-inconsistent things as of the latest ES6 spec:
Various typed array things do `ToPositiveInteger`, a new operation as of ES6: - `ArrayBuffer(length)` and `TypedArray(length)` - Constructing a typed array, and `TypedArray.prototype.set`, coerce both the passed object's `length` property and the numeric byte-offset argument - Most interestingly, `TypedArray.prototype.@@elementGet(index)` and `@@elementSet(index, value)` do a `ToPositiveInteger` on `index`. So `typedArray[-123] === typedArray[0]`, and `typedArray[-321] = 5` gives `typedArray[0] === 5`. Whereas arrays use `ToUint32`, but sometimes throw `RangeError`s: - Indices generally "work" if `ToString(ToUint32(index)) !== index`; otherwise they're treated as ordinary properties. - When getting a length from any array-like, you just do `ToUint32` on it. - But when setting a length, you validate so that if `ToUint32(length) !== length`, a `RangeError` is thrown. Finally, one lone place throws `RangeError`s after conversion: - `String.prototype.repeat(count)` throws if `ToInteger(count)` is negative or infinite. --- I was curious if there were any interesting rationales driving these decisions. (And I fully appreciate there might not be; it could just be compatibility constraints.) Or, to put it another way, I was curious what would be considered "idiomatic" JS, e.g. in the same way that the spec sets a precedent of `ToString`-ing all string inputs to its functions. _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
