Output an Object vs a Map

[bmeck]

With a Map, grouping don't have to be on key compatible types and avoids coercions:

o = {};
o[1000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000] = 1;
Object.keys(o); // ["1e+90"]

Using an object knowledge of key coercion might be a bit odd.

Problems with Map are usability on reading data out of the Map not being simple property access though but you can always Object.fromEntries(map).

[ljharb]

This came up briefly in plenary. Maps are simply not ergonomic enough to be the primary return type for this API - like it or not, object are the way people pass around data, and property key conversion is a non-issue for most use cases (and is pretty commonly understood, imo)

#3 covers adding a secondary way to get a Map out, for those that want it.

[bmeck]

seems fine, I wouldn't call it understood though