Last week I visited the React Europe conference in Paris; it was the first such event in Europe and the second React conference in the world. Paris like much of the rest of western Europe during this early July was insanely hot. The airconditioning at the conference location had trouble keeping up, and bars and restaurants were more like saunas. Nonetheless, much was learned and much fun was had. I'm glad I went!

React, in case you're not aware, is a frontend JavaScript framework. There are a lot of those. I wrote one myself years ago (before it was cool; I'm a frontend framework hipster) called Obviel. React appeals to me because it's component driven and because it makes so many complexities go away with its approach to state.

Another reason I really like React is because its community is so creative. I missed being involved with such a creative community after my exit from Zope, which was due in large part as it had become less creative. A lot of the web is being rethought by the React community. Whether all of those ideas are good remains to be seen, but it's certainly exciting and good will come from it.

Here is a summary of my experiences at the conference, with some suggestions for the conference organizers sprinkled in. They did a great job, but this way I hope to help them make it even better.

Hackathon When I heard there would be a hackathon the day before the conference, I immediately signed up. This would be a great way to meet other developers in the React community, work on some open source infrastructure software together, and learn from them. Then a few days before travel I learned there was a contest and prizes. Contest? Prizes? I was somewhat taken aback! I come from the tradition of sprints in the Python world. Sprints in the Python community originated with the Zope project, and go back to 2001. Sprints can be 1-3 day affairs held either before or after a Python conference. The dedicated sprint is also not uncommon: interested developers gather together somewhere for a few days, sometimes quite a few days, to work on stuff together. This can be a small group of 4 people in someone's offices, or 10 people in a converted barn in the woods, or 30 people in a castle, or even more people in a hotel on a snowy alpine mountain in the winter. I've experienced all of that and more. What do people do at such sprints? People hack on open source infrastructure together. Beginners are onboarded into projects by more experienced developers. New projects get started. People discuss new approaches. They get to know each other, and learn from each other. They party. Some sprints have more central coordination than others. A sprint is a great way to get to know other developers and do open source together in a room instead of over the internet. I previously thought the word hackathon to be another word for sprint. But a contest makes people compete with each other, and a sprint is all about collaboration instead. Luckily I chatted a bit online before the conference and quickly enough found another developer who wanted to work with me on open source stuff, turning it into a proper sprint after all. We put together this little library as a result. I also met Dan Abramov. I'll get back to him later. When I arrived at the beautiful Mozilla offices in Paris where the sprint was held, it felt like a library -- everybody was quietly nestled behind their own laptop. I was afraid to speak, though characteristically that didn't last long. I may have made a comment that I thought hackathons aren't supposed to be ibraries. We got a bit more noise after that. I thoroughly enjoyed this sprint (as that is what it became after all), and learned a lot. Meanwhile the hackathon went well too for the three Dutch friends I traveled with -- they won the contest! React Europe organizers, I'd like to request a bit more room for sprint-like collaboration at the next conference. In open source we want to emphasize collaboration more than competition, don't we?

Conference The quality of the talks of the conference was excellent; they got me thinking, which I enjoy. I'll discuss some of the trends and list a few talks that stood out to me personally; my selection has more to do with my personal interests than the quality of the talks I won't mention, though. Inline styles and animations Michael Chan gave a talk about Inline Styles. React is about encapsulating bits of UI into coherent components. But styling was originally left up to external CSS, apart from the components. It doesn't have to be. The React community has been exploring ways to put style information into components as well, in part replacing CSS altogether. This is definitely a rethinking of best practices that will cause some resistance, but definitely very interesting. I will have to explore some of the libraries for doing this that have emerged in the React community; perhaps they will fit my developer brain better than CSS has so far. There were two talks about how you might define animations as well with React. I especially liked Cheng Lou's talk where he explored declarative ways to express animations. Who knows, maybe even unstylish programmers like myself will end up doing animation! GraphQL and Relay Lee Byron (creator of immutable-js) gave a talk about GraphQL. GraphQL is rethinking client/server communication originating at Facebook. Instead of leaving it up to the web server to determine the shape of the data the client code sees, GraphQL lets that be expressed by the client code. The idea is that the developer of the client UI code knows better that data they need than the server developer does (even if these are the same person). This has some performance benefits as well as it can be used to minimize network traffic. Most important to be me is that it promises a better way of client UI development: the data arrives in the shape the client developer needs already. Lee announced the immediate release of a GraphQL introduction, GraphQL draft specification and a reference implementation in JavaScript, resolving a criticism I had in a previous blog post. I started reading the spec that night (I had missed out on the intro; it's a better place to start!). Joseph Savona gave a talk about the Relay project, which is a way to integrate GraphQL with React. The idea is to specify what data a component needs not only on the client, but right next to the UI components that need it. Before the UI is rendered, the required data is composed into a larger GraphQL query and the data is retrieved. Relay aims to solve a lot of the hard parts of client/server communication in a central framework, making various complexities go away for UI developers. Joseph announced an open source release of Relay for around August. I'm looking forward to learn more about Relay then. Dan Schafer and Nick Schrock gave a talk about what implementing a GraphQL server actually looks like. GraphQL is a query language, not a database system. It is designed to integrate with whatever backend services you already have, not replace them. This is good as it requires much less buy-in and you can evolve your systems towards GraphQL incrementally -- this was Facebook's own use case as well. To expose your service's data as GraphQL you need to give a server GraphQL framework a description of what your server data looks like and some code on how to obtain this data from the underlying services. Both Dan and Nick spent the break after their talk answering a lot of questions by many interested developers, including myself. I spoke to Dan myself and I'm really grateful for all his informative answers. The GraphQL and Relay developers at Facebook are explicitly hoping to build a real open source community around this technology, and they made a flying start this conference. Flux All this GraphQL and Relay stuff is exciting, but the way most people integrate React with backends at present is through variations on the Flux pattern. There were several talks that touched upon Flux during the conference. The talk that stood out was by Dan Abramov, who I mentioned earlier. This talk has already been released as an online video, and I recommend you watch it. In it Dan develops and debugs a client-side application live, and due to the ingenious architecture behind it, he can modify code and see the changes in the application's behavior immediately, without an explicit reload and without having to reenter data. It was really eye-opening. What makes this style of development possible is a more purely functional approach towards the Flux pattern. Dan started the Redux framework, which focuses on making this kind of thing possible. Instead of definining methods that describe how to store data in some global store object, in Redux you define pure functions instead (reducers) that describe how to transform the store state into a new state. Dan Abramov is interesting by himself. He has quickly made a big name for himself in the React community by working on all sorts of exciting new software and approaches, while being very approachable at the same time. He's doing open source right. He's also in his early 20s. I'm old enough to have run into very smart younger developers before, so his success is not too intimidating for me. I'll try to learn from what he does right and apply it in my own open source work. The purely functional reducer pattern was all over the conference; I saw references to it in several other talks, especially Kevin Robinson's talk on simplifying the data layer, which explored the power of keeping a log of actions. It has its applications on both clients and servers. The React web framework already set the tone: it makes some powerful functional programming techniques surrounding UI state management available in a JavaScript framework. The React community is now mining more functional programming techniques, making them accessible to JavaScript developers. It's interesting times. Using React's component nature There were several talks that touch on how you can use React's component nature. Ryan Florence gave an entertaining talk about you can incrementally rewrite an existing client-side application to use React components, step by step. Aria Buckles gave a talk on writing good reusable components with React; I recognized several mistakes I've made in my code and better ways to do it. Finally in a topic close to my heart Evan Morikawa and Ben Gotow gave a talk about how to use React and Flux to turn applications into extensible platforms. Extensible platforms are all over software development. CMSes are a very common example in web development. One could even argue having an extensible core that supports multiple customers with customizations is the mystical quality that turns an application into "enterprise software".

DX: Developer Experience The new abbreviation DX was used in a lot of talks. DX stands for "Developer Experience" in analogy with UX standing for "user experience". I've always thought about this concept as usability for developers: a good library or framework offers a good user interface for developers who want to build stuff with it. A library or framework isn't there just to let developers get some done, but to let them get this stuff done well: smoothly, avoiding common mistakes, and not letting them down when they need to do something special. I really appreciated the React community's emphasis on DX. Let's make the easy things easy, and the hard things possible, together.

Gender Diversity This section is not intended as devastating criticism but as a suggestion. I'm not an expert on this topic at all, but I did want to make this observation. I've attended a lot of Python conferences over the years. The gender balance at these conferences was in the early years much more like the React Europe conference: mostly men with a few women here and there. But in recent years there has been a big push in the Python community, especially in North America, to change the gender balance at these conferences and the community as a whole. With success: these days PyCons in North America attract over 30% women attendees. While EuroPython still has a way to go, last year I already noticed a definite trend towards more women speaking and attending. It was a change I appreciated. Change like this doesn't happen by itself. React Europe made a good start by adopting a code of conduct. We can learn more about what other conference organizers do. Closer to the React community I've also appreciated the actions of the JSConf Europe organizers in this direction. Some simple ideas include to actively reach out to women to submit their talk and to reach out to user groups. Of course, for all I know this was in fact done, in which case do please do keep it up! If not, that's my suggestion.