[dev-platform] Intent to prototype: Object.hasOwn

[Yulia Startsev]

Hi Everyone,

This proposal adds to JavaScript an ergonomic way to check if a property exists directly on an object, and not on it's prototype chain. It is a small proposal, but this is tricky to get right, as it will throw on objects such as Null.

A common implementation is:

let hasOwnProperty = Object.prototype.hasOwnProperty

if (hasOwnProperty.call(object, "foo")) {
  console.log("has property foo")
}

Which can now be simplified to

if (Object.hasOwn(object, "foo")) {
  console.log("has property foo")
}

Bug: Bug 1711872
Standard: Spec text, Proposal

Platform coverage: All.
Preference: None, available only on Nightly.
DevTools bug: None.
Other browsers:

1. Google Chrome supports this behind a flag --harmony-object-has-own

2. Safari: Not supported yet

Test262: Tests are in progress and will be merged when they land.

best,

Yulia