Prototype definition in object literal

@kaizhu256 - I've actually started a separate thread over here that discusses the importance of inheritance in Javascript. I do beleive in the current state of Javascript, there are certain scenarios where inheritance can be useful, but I also think it does get overused often, and there's potentially different ways to model the language in it's future so that we don't need inheritance at all. Certainly, some of your examples would fall into the overused cases. If you have thoughts related to the overall value of inheritance, you could add to the discussion there. But, like @ljharb said, we've got to keep in mind that Javascript is used by people for all sorts of purposes. It's not simply used by front-end devs to add a tiny bit of scripting to an almost static page - highly interactive webpages, webapps, servers, scripts, electron apps, etc, all require a different level of complexity, and the language has to support all of these use cases. Those who only need the most basic features from Javascript can cherry-pick those out and use them, but for everyone else who needs a little more power, the committee is committed to providing that kind of power for everyone.

For the purposes of this post, it's probably best to just assume that is the occasional valid use case for inheritance (what those are can be discussed in the other thread).