[esmooov]

This is exactly what PourOver offers. You can chain filter results to any boolean complexity, as well extend the default filter types to optimize indexing and caching. Indeed, PourOver was trivial to make, an outgrowth of the very pattern you define above. PourOver is just an attempt to scrap that boilerplate, allow for the queries to be indexed, combined with sorts, and automatically rebuild when the collection changes.

[nathanhammond]

Thinking about it more, I believe that my visceral reaction was to the imperative nature of the library. I was imagining trying to code something that generated a filter (e.g. PourOver.makeExactFilter("mythology", ["greek","norse"]);) and it seems like it would be unnecessarily complex without data-binding propagation/invalidation.

If I wanted to add "roman" mythology to that filter I would imagine something like:

    var mythologies = ["greek", "norse"];
    // ... create a collection with filters
    mythologies.push("roman");
    PourOver.makeExactFilter("mythology", mythologies);

But you don't get that last statement for free, nor the one where you join it into a collection, nor do I see a way to replace the previous mythologies filter. Any time you need to reprocess a filter you've got to run it through a series of imperative actions triggered from one of the events, and possibly throw away the collection and regenerate it (if you can't remove disjoint filters).

I would be pushing for a Object.observe/dirty checking/get-set version of this to take PourOver to the next level of utility. (?/Angular/Ember)

[esmooov]

I think I'm a little confused. Why wouldn't you have just added the "roman" possibility from the get go? Could you provide an example of a situation when you don't know the universe of possibilities in advance?

[rattray]

If the user adds one, or new data enters from an outside source (pub/sub, sockets, etc)

[esmooov]

Alright, this is a great point. It would be trivial for me to add addPossibilities. I think I'll do that! Thanks. This will really help for using PourOver to power tagging selection fields where you can ... add possibilities!

[nathanhammond]

Exactly what @rattray said. It's something you get nearly for free in data-binding world and is much harder to accomplish in imperative code. I wish you luck, and make sure you blog about it when it's done! (I want to see how it's implemented.)