Use an interface for ContactInfo & set unrequested fields to null.

[rayankans]

Using an interface would help with issue #19, since we would be able to check if a certain property is supported by the browser. It was also the result of some conversation in #21

[beverloo]

I like that this enables per-property feature detection.

With the default serializer behaviour, the following would happen:

const data = await navigator.contacts.select(['tel']);
console.log(JSON.stringify(data));

[
  {
    "email": null,
    "name": null,
    "tel": ["+442079460789"]
  }
]

That seems rather wasteful, particularly when multiple contacts are being selected, or when more fields may be added to the API. Would it be fair to teach a new ContactInfo about the properties passed to the select() call? It feels a bit hackish.

@domenic wdyt, given that you suggested moving to dictionaries in #5?

[domenic]

I still believe that for data that does not have behavior (e.g. methods), a dictionary should be strongly preferred. I do not support moving in this direction.

[yoavweiss]

@rayankans - Can you join the WICG in order to appease the IPR bots?

[rayankans]

We could potentially have use a non-default toJSON implementation that ignores null values, but yeah using a dict seems cleaner at this point.