It's always been clear that React alone isn't enough to write a full application; you need to combine it with some other pieces. The official recommendation from Facebook is to use flux, and the most popular flux implementation (redux) is quite good, but you can also use Om-style approaches (Omniscient, Baobab, etc.), or wire it up to legacy Backbone models, or whatever. But you need something; you can't write an MVC app with only the V and expect good results.
You guys tried to write a large "pure" React application, and it failed in all the ways that large React applications always fail. And you learned from it, and hacked together a kinda-sorta-fluxish solution, and it's working for you, and that's great.
...but if you want to take another look at it someday, I'd highly suggest checking out redux. It's very slick, and it was explicitly designed to solve the exact issues you ran into.
(In particular, a redux app is built of a small number of smart components which respond to to a specific subset of events, each managing a tree of "dumb" components, which gives you the granularity you were looking for. And then you can use the PureRenderMixin and immutable data, which gives you the very fast shouldComponentUpdate methods you were looking for for free, no need to ever write your own since, as you found, that way lies madness. The docs even cover how to properly cache derived data, another issue you noted running into. And so on.)
(...of course, that doesn't really tell you much about React; seems like all you really learned is that badly architected apps perform badly. Not sure that one needed much testing. And of course, your initial comment seemed to be making a very different claim.)
In any case, our current view is that there is a useful middle ground where React may work well for us. The app in question predates just about all of the modern JS UI libraries/frameworks, at least in anything close to their current forms, so much of the rendering and event management code right at the front end is built with jQuery, early toolkits, and in many cases a lot of home-grown code. All of this still works pretty well, but quite a large proportion of it is functionality that every UI library in the universe provides today, so there's little reason to maintain another version any more. The rest of the app does have a good architecture that has stood the test of time, but for the next big update we're trying to solve much the same issues as everyone else with managing UI code as the app grows.
React is of interest to us for several reasons, from being a useful templating mechanism, through providing a way of composing components that are relatively clean and modular in design, to its efficient DOM updates and declarative nature. These too are presumably the features that make it attractive to many of its users. But it is also of interest for this project precisely because its scope is tightly confined to just the rendering parts of the system and it doesn't try to lock the whole app into its own framework.
We just confirmed early that some of the hype really is only that, and that scaling up to the kind of UI that has more than a few hundred data points on screen at one time is not as easy as some of the advocacy might suggest, so we're exploring how we can use the tool to take advantage of what it clearly does offer and play to its strengths without paying too high a price. In that respect, it's really no different to any other library we'd evaluate.
That's a bit No True Scotsman for me. Just in the replies to my previous comment, there are several quite clear yet apparently contradictory views expressed about how these things are supposed to work. I doubt that anyone, probably including the React developers themselves, yet has enough experience to sensibly determine what is and isn't idiomatic or best practice here. In any case, I'm far more interested in effective results than dogma, which is why we've been doing practical investigations into what really happens when the tools are used in different ways.
Conceptually, you should be running render() methods on the actual items which have changed, and a very small number of parent components with little-to-no DOM elements. You should also be executing a relatively small number of shouldComponentUpdate() methods which should be extremely fast to execute.
And this is where the assumptions started breaking down in our experiment.
For one thing, we have a somewhat complicated data model and a somewhat complicated UI to present it. Managing the relevant shouldComponentUpdate mechanisms was getting tedious even in our short term experiment. If you're rerendering top-down in a heavily nested UI then it seems you need to provide shouldComponentUpdate in quite a lot of places just to deal with the parent-child relationships with acceptable efficiency, and each of those implementations is a potential source of errors because now you have multiple sources of truth.
Also, for things that aren't extremely fast to execute because they rely on derived data, you wind up with questions of what intermediate results to cache and where. Caching intermediate results goes against the kind of approach much of the React community seems to advocate, hence props in getInitialState being an antipattern and all that.
Time will tell, but once the abstraction started leaking in these kinds of ways, it wasn't clear to us that trying to follow the pure, declarative approach that a lot of React advocacy promotes was really better than other strategies.
If you are doing that, then where exactly was the performance bottleneck, and how was your alternative approach avoiding it?
Bottlenecks were as above, among others.
Avoiding them comes down to the simple principle that if each component attaches to listen to events in a modular way and sets its own state accordingly, then the default is essentially not to rerender anything and has zero overhead. As soon as you start making active decisions about what to rerender, you immediately have the overhead of those decisions to worry about, and sometimes that overhead is significant if you're, say, responding to every character typed in a text box.
If you respond at a more local level, you can choose the granularity of responses to keep the overheads more controlled, which it seems so far is effectively getting the best of both worlds.
In fact, it sounds like your second approach might be closer to a normal idiomatic React app than your first implementation. Incidentally, are you using some sort of flux architecture?
In the sense that user interactions send meaningful messages to an internal component, that component is responsible for updating some stored data accordingly, and the internal component then signals changes that other parts of the UI can respond to, yes, it's somewhat like Flux in overall architecture.