Should array-like argument be permitted?

[bathos]

Currently it’s expected that the argument to Object.fromEntries be an iterable in the Symbol.iterator sense.

The Array.from and %TypedArray%.from methods permit array-like arguments; they fall back on looking for an appropriate length property and numeric keys. Because the ToLength operation coerces most values to 0, this means that they will also accept most objects:

Array.from({}) // []
Array.from({ length: 1 }) // [ undefined ]
Array.from({ length: Infinity }) // RangeError

My sense (which might be wrong) is that support for array-likes was a way to help bridge the gap with pre-ES2015 APIs. Should a new "from" method also support array-likes, or should it be limited to formal iterables like the Map and Set constructors?

See #8 (comment)

[ljharb]

This is a good question, but I don't think it's actually necessary to accept arraylikes.

[zloirock]

See this issue tc39/proposal-setmap-offrom#3

[bathos]

Great link! Closing, seems clear that genuine iterables are all we should accept.

[ljharb]

This is a good question, but I don't think it's actually necessary to accept arraylikes.

[zloirock]

See this issue tc39/proposal-setmap-offrom#3

[bathos]

Great link! Closing, seems clear that genuine iterables are all we should accept.