- Originally, the game was rendered with SVG elements, so it was very important to use the shouldComponentUpdate hook to ensure elements weren't rendering unnecessarily (and using CSS transformations to position them where possible, as that's way faster than updating SVG coordinates!)
- I had something similar to the function.bind problem since some of my components had a map of hotkey handlers that I was (naively) returning from a `getHotKeyHandlers` function, meaning the handlers were redefined every render.
- I wasn't caching/memoizing calculations done to the Redux state as well as I should have (Reselect is very useful for this!)
I ended up deciding SVG wasn't fast enough for my use case and rewriting the core game loop rendering to use Canvas, which was so much faster that I could be a lot lazier about optimizing things. Everything around the canvas is still rendered through React components (i.e. in game UI and menu screens), and the state is still handled through Redux. It's a very fun way to write a game :)
I've still not had a chance to play around with it, but the Flipboard mobile site looks phenomenal.
Currently, my biggest 'bottleneck' when developing React applications is managing complex forms. Right now I'm using redux-form  which is a great tool, but not very performant on dynamic deep/complex forms (more info and partial hacks here: ).
Other than that, I don't have performance problems, but I'm curious when will I hit Redux limitations (single store sounds great from the conceptual point of view, but I'm not sure about the performance one). Also, can second ImmutableJS recommendation, after a while of using it's completely natural to use.
I use redux on our newest application and so far have been very happy with it. Previously I was using the `flux` facebook library. Flux was also good, but there was a lot of boilerplate for creating new stores.
Redux is nice because your 'containers' (smart-components that `connect` to the store via `react-redux`) only consume the slice of state that they need. My store is pretty big, but the Settings page, for example, only needs the userId from the store. Redux optimizes for that. The single-store has actually greatly simplified the whole process without any noticeable performance hits.
But the Redux "single store" is actually a composition of multiple stores, each with its own reducer function. Performance-wise, it's actually better than vanilla Flux, because, when an action causes N stores to change with vanilla Flux, you can get up to N renders of your components (depending on how many stores they subscribe to). At least, with Redux there is only one render when the whole store has been updated.
But I agree, it's still not perfect. You avoid doing the more expensive virtual DOM comparison, but you still have to iterate over all the items to do the PureRenderMixin checks. And it is still O(n) time, just with a smaller constant.
Another solution is to not actually render all the children, just the ones that are visible on the screen, i.e. using some React implementation of infinite lists (see: https://facebook.github.io/fixed-data-table/ )
Another idea that I've been thinking about is to arbitrarily fragment your list into lists (possibly of fixed size, or a fixed number of fragments). Each fragment gets its own subcomponent, so we can avoid rendering fragments that haven't changed. For example, instead of a list of 100 items, we treat it as 10 lists of 10 items. If we change one item, we end up instantiating 10 components, and then recursing into the single fragment that has changed, instead of over all 100 items.
I tried to implement one by representing the text as a long list of character components, thinking react could handle this by only executing small incremental updates, but the whole thing became slow anyway.
Am I missing something, or is react not up to this task?
There are open-source projects worth looking at like Ritzy which is quite fast and written in React from what I've read.
As per your specific issue, I've found that using PureRenderMixin with each line of text represented as a component works for hundreds of lines, but this still ends up with performance issues as you scale to thousands of lines. Using a list of one-character components will run into performance issues much sooner as there is per-component overhead.
It's tiny but offers a number of utilities that are more convenient than what you get with ES6 spread syntax. The tradeoff with Immutable.js is that if you have huge single objects (arrays with many elements, objects with many keys), then making copies will get more expensive than with Immutable. Otherwise, icepick is all win.
To re-iterate the possible solutions I've considered:
- Don't pass in a bound method; give the component the unbound method and its index and the child component can call it with the index passed in itself.
- Generalize this to a re-usable intermediary component that does for you (it does feel a bit dirty)
- Write your own bind function that annotates the bound function with original function + params allowing you to do a "deep" equality check, and then use a variant of PureRenderMixin that does this "deep" equality check.
Honestly, all of the solutions feel a bit hacky, but I've gravitated towards the first and second options.
What do you use for state management? Flux, alt, redux, something else?
Thank you for sharing your experience and tips regarding developing React apps!
Our front-end stack was primarily just webpack (no JSX because CoffeeScript's terseness sufficed). We recently started the migration to using Babel with ES6 and JSX because of the linting / tooling / community behind them.
I will be sharing a more in-depth look at my debugging workflow in the next post, so be on the lookout :-)
> Also any recommendations for performant charting/graphing library that plays well with React?
I haven't used many charting / graphing libraries, sorry!
> What do you use for state management?
We were fairly early adopters to React and Flux, so we have our own internal implementation of Flux. I haven't worked too much with the other state management solutions, but many of them seem like good, opinionated architectures.
> Thank you for sharing your experience and tips regarding developing React apps!
No problem :-)
0. shouldComponentUpdate (SCU) is everything. Consider creating a base React.Element extension class. I define a base shouldComponentUpdate and some useful utilities on it. Having it in one place is really useful because you can log its output from every component and watch how your whole application updates. It makes it easy to see useless rerenders.
- One very helpful addition in our app has been a static 'SCUSelector' property, which tells our shallow shouldComponentUpdate to ignore certain props/state/context. This helps in combination with rich componentWillMount() or getInitialState() functions to precalculate expensive data that updates rarely/never.
1. It seems the `connect(component, selector)` model  encouraged by Redux to hook up application data to deep(er) components is much better for performance. You want to avoid renders in as many tree branches as possible. To this day, the root element (`<App>`) still holds most of our data and fans it out to the Router, Header, Sidebar, etc. This root-level render must be extremely fast because it runs on every tick. Hoisting any and all data that can be made constant is a huge help.
2. We saw massive (50%+) performance gains from Babel's constant-elements and inline-elements optimizations . Careful with it - there's is a nasty bug  that only manifests in production you need to be aware of if you're deploying this.
3. Immutable-JS is kind of a wash. I'm not a big fan of the API or how easy it is to nest mutable objects and arrays inside immutables. The new array/object spread syntax in ES6 makes it easier to construct unique objects every time data updates, so you can do a shallow shouldComponentUpdate.
4. Watch out for function identity because it will blow SCU . Either ignore the property explicitly, or use a binding helper like the one I posted on that issue .
5. If you're doing expensive data computation, such as update/insert/delete/image on websockets, profile it. If you're accidentally causing deopt, you'll feel it. Make sure the libraries you use don't cause deopt either. A few simple tweaks  can give you 2-10x performance boosts on hot functions .
6. If you haven't already, watch videos on how V8 optimizes. It will help you write fast code in the future.
7. Keep watching your app! The new React devtools can highlight components as they update. This is really useful to see what work is being done and how you can improve.
This is bit meta, but it's really, really awesome to see an article on performance begin with this. Well done author :-)
It instantly inspires confidence that the material to follow is worthwhile reading. Knowing the author has started out with this philosophy I trust more that what's covered will focus on things that actually matter, rather than just being a crawl through every and any technique or quirk that they've come across, regardless of its relative impact.
Performance is one of those things where more is obviously better, all other things equal, but that last 20% of effort invested is almost always time that could be better spent improving other aspects of the average use case of any given product, let alone the average product.