Introduce dynamicObject for dynamically keyed objects in Proxy supporting environments

[mweststrate]

See also #336

Introduce object = dynamicObject(object) and implement that using ES6 proxies. This allows plain objects to be used as observable objects, without the current limitation of not supporting dynamic keys.

I think that is a nice case to start working with Proxies, learn about their caveats, performance etc. It has a clear use case and advantage over the current getter / setter implementation, yet there is a fallback for those needing to support browsers without proxies (probably the most of us): ObservableMaps

Example:

const todos = dynamicObject({
  "a23bf": { completed: false}
})

autorun(() => console.log(Object.keys(todos)))
// prints "a23bf"

todos["a8235"] = { completed: true}
// prints "a23bf", "a8235", something that currently can only be achieved through observable maps

Should throw clear error if proxies (or too limited polyfill) are not available at runtime and hint at using ObservableMaps instead

[mull]

Did anyone start working on this yet?

[amir-arad]

I have #776 with pending tasks, but it's not going to get any serious boost from my end

[ascoders]

Hi @mweststrate , I implemented mobx in proxy, although not all of the API has been implemented, but the core functionality has been opened and has passed 50 unit tests and has been run online.

code: https://github.com/ascoders/dynamic-object

[ascoders]

And implemented a similar mobx-react called dynamic-react, i wish I could merge into mobx

[mweststrate]

@ascoders didn't see the comments earlier, thanks! Will check the code out when starting on proxies.

Closing this issue now in favor of #1076