Add deleteProperty to TrackedObject

[sukima]

Allows to do delete this.myTrackedObject.foo or Object.deleteProperty(this.myTrackedObject, 'foo').

[pzuraq]

This seems good! Will merge once tests are passing, thanks for taking this on!

It's worth noting that delete is a pretty expensive operation usually, so it's something you may want to avoid, but it's in line with the philosophy of tracked-built-ins to support all possible operations transparently

[gnclmorais]

It's worth noting that delete is a pretty expensive operation usually (…)

@pzuraq, is there a lighter alternative when you want to remove a key from an onbject? For example, is creating a new object with all the original keys minus the one we want to remove “cheaper”?

[gnclmorais]

@sukima, the build is now fixed, so feel free to rebase master onto your branch to get this going. 😃

[pzuraq]

@gnclmorais generally it's a bad idea to change the shape of an object, either by adding or removing fields, because the engine will optimize access to the fields based on the shape of the object. Deleting a key both changes the shape, and I believe transitions the object into dictionary-mode, which is even worse performance because then it essentially doesn't have a shape at all, and every access is less optimal.

If you are adding/removing keys regularly, I tend to recommend using a Map instead of an object, because they are built for that. Another option is to do Object.create(null), which I puts the object directly into dictionary mode.

I also generally strictly separate my dictionaries/maps, which have mutable shapes, from classes or object literals, which I ensure always have the same shape.

[boris-petrov]

This PR fixes #27 and is doing the same thing as #30.

[gnclmorais]

@pzuraq, thank you for your answer, quite insightful and gave me some food for thought!

[nag5000]

Hmm, according to the spec, deleteProperty has no receiver.

[gnclmorais]

True if you look at an Object’s deleteProperty, but in this case, we’re dealing with a Proxy.

[nag5000]

I'm sorry, but I don't really understand. What is "Object's deleteProperty"?
I meant proxyHandler.deleteProperty has no receiver argument, tc39/ecma262#1198

[gnclmorais]

I think you’re right, @nag5000. 👍 I got confused.

[chriskrycho]

Happy to land this (presumably as a minor release after the major I'm releasing today). This could use a rebase and for the last couple comments to be addressed, however.

[chriskrycho]

Closing this in favor of the slightly cleaner implementation in #30. Thanks!