Arrays, symbols, and realms

On Twitter, Allen Wirfs-Brock asked folks if they knew what Array.isArray(obj) did, and the results suggested… no they don't. For what it's worth, I also got the answer wrong. Type-checking arrays Let's say we wanted to do something specific if obj is an array. JSON.stringify is an example of this, it outputs arrays differently to other objects. We could do:

[efcl]

instanceofはrealm(iframe)で異なるものとなる。 `Array.isArray`は内部データを見るためrealmsは関係ないが、それはArrayのメソッドを持ってることを意味しない。 一方Symbolはrealmを超えて共通なので、これを使って判定する話