Support for Object.hasOwn()

[andrewreedy]

Missing/Incorrect APIs

Are there plans to support Object.hasOwn()?

Relevant documentation

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwn

[noppa]

Would be pretty awesome if this would also work as a refinement for optional properties

type A = { foo?: string }
declare var a: A

if (Object.hasOwn(a, 'foo')) {
  a.foo.toUpperCase() // this is fine
}

[pascalduez]

Added in #9084

Although it's not refining in it's current state... try flow

[noppa]

I wasn't able to make this using string key arg in the second argument, but you can make a similar function that refines a bit if you change the API to accept object as the second arg and take keys from there, similarily to what could be used as a typesafe userland Pick until the native version landed

if (hasOwnProperties(a, {foo: 0})) {
  a.foo.toUpperCase()
}

Try flow.

Doesn't work with object union types, though.