Everyone should just play nice with each other. But instead, we have dudes like this guy "Evan", who run around and spill negative, toxic chaos everywhere. Evan thought he'd play a "game" with his friends by bullying a Tinder match for the way she looked, from afar. 

Well, that whole operation definitely went on to catch up with him. I would've loved to have seen that date going down, as it experienced all the (intentional) customer service disasters. I wonder if there was ever a point where it occurred to the dude, "man I wonder if all my negativity is catching up with me?" Maybe, so. 

Oh man, "Chad the Alpha" is on one. This conversation just stinks of delusions. Alpha bro reaches out to another dude and literally asks him to break up with his girlfriend, because he suspects that she'll be happier with him. Yeah, okay, Chad. 

Man, just imagine walking around and seeing one of these mannequins in one of these bizarre positions, and the reality trip that that'd throw you for? A definite double take would be in order. Can imagine the cops being called on some of these. Mannequins are already eerie enough as it is. 

This guy got challenged to make music with bricks, so he went ahead and played The Weeknd's "Blinding Lights" with bricks. Um, that's amazing. Had no idea that was possible. 

NOTE: In our traditional April Fool’s posts, we endeavor to make them credible at the beginning, then crank up the nonsense until the joke becomes obvious. But these days, the idea of knowingly spreading misinformation (even when comically false) sounds exhausting. So here’s our notice ahead of time: This is 100% silliness! Hope it lightens [...]

Thousands of babies were born with severe brain damage after the 2015 Zika outbreak. New findings could tell us which therapies could help them most

We know that there is at least one planet orbiting Proxima Centauri, the nearest star to our solar system, and now astronomers may have taken the first picture of a second world

A brain-computer interface has helped a man with a severe spinal cord injury move and feel using a hand again, letting him carefully lift light objects such as a paper cup

Many people are turning to virtual therapy and mental health apps to cope with the stress of the coronavirus pandemic, but they may not be as helpful as talking face to face

Lessons learned from natural disasters and the military can help guide our responses to help people's mental health during the covid-19 pandemic

Robots made of 3D-printed muscle and rat spines could help us understand conditions like motor neurone disease and the technique may eventually be used to build prosthetic devices

It can be difficult for doctors to assess the level of consciousness in people who have had serious brain injuries, but observing their reaction to strong odours may help

A robot that uses artificial intelligence to find and remove weeds could eventually be used as an alternative to chemical insecticides

A fresh look at the world’s oldest religious texts suggests ancient Egyptians saw the sky as a water-filled iron container from which chunks fell to Earth as meteorites

Astronomers found a star that appeared to be orbiting nothing at all – but it’s actually the closest black hole ever at just 1000 light years away

Many ancient monuments are claimed to be aligned to celestial phenomena, but we now have the first statistical evidence this is the case for the Egyptian pyramids

The latest coronavirus news updated every day including coronavirus cases, the latest news, features and interviews from New Scientist and essential information about the covid-19 pandemic

You have to give a lot of credit to Tim Bray, an Amazon vice-president who quit over the company’s treatment of workers. He was making a big sacrifice to expose Amazon’s corruption. May 1st was my last day as a VP and Distinguished Engineer at Amazon Web Services, after five years and five months of […]

Contrary to popular belief, people do order fish sandwiches at Arby's.Senate Democrats recently learned one of their own is among that rare crowd when Sen. Joe Manchin (D-W.V.) forgot to hit mute when driving through an Arby's drive-through last month. Manchin pulled up to the fast food spot in his home state, asked for a King’s Hawaiian Fish Deluxe sandwich, and later learned his mistake after staffers texted him, he tells The Wall Street Journal."It's a big piece of fish and it has a big slice of cheese," Manchin described to the Journal. "They were just jealous they weren't getting the good sandwich." Manchin himself may be jealous that unlike West Virginia Gov. Jim Justice, he doesn't have a sandwich named after him at his local Arby's.Manchin is far from the only lawmaker who's been "busted," as he put it, for forgetting to hit mute. Rep. Jamie Raskin (D-Md.) says his children have repeatedly walked by and told him to "tell [House] Speaker [Nancy] Pelosi to say now is the time to start forgiving student loans." Several described overhearing "colleagues exercising on ellipticals, doing sit-ups, dealing with children, or taking other phone calls," they tell the Journal. And many of them have admittedly skipped showers on days they know they don't have to be on camera. Read more about congressmembers' at-home habits at The Wall Street Journal.More stories from theweek.com The full-spectrum failure of the Trump revolution Unemployment is a catastrophe — but it could still be worse Trump reportedly got 'lava level mad' over potential exposure to coronavirus

Experts still aren't sure why some coronavirus cases are so much worse than others, but the answer may lie in patients' genetic differences.

On Thursday, the country reported its largest one-day increase in new cases of 11,231 — yet President Putin already has his eyes on reopening.

People celebrate VE Day across Britain, following Germany's surrender in 1945.

Footage of last year's Red Square military parade play on TV as the pandemic mutes celebrations.

Andrew's mother was dying in hospital under lockdown, so he used technology to spend time with her.

As coronavirus spreads in the provinces, more and more health workers are getting sick - and dying.

People have been dedicating their workouts to Ahmaud Arbery who was shot and killed while out jogging.

Jen was present for, and actively participated in, the very beginnings of the creative and blogging web, and her famous book, now in its umpteenth edition, is still the best introduction to web design I know—probably the best that will ever be written.

The post My Brunch with Jen appeared first on Zeldman on Web & Interaction Design.

To share upcoming changes with our partners in the React ecosystem, we’re establishing official prerelease channels. We hope this process will help us make changes to React with confidence, and give developers the opportunity to try out experimental features.

This post will be most relevant to developers who work on frameworks, libraries, or developer tooling. Developers who use React primarily to build user-facing applications should not need to worry about our prerelease channels.

React relies on a thriving open source community to file bug reports, open pull requests, and submit RFCs. To encourage feedback, we sometimes share special builds of React that include unreleased features.

Because the source of truth for React is our public GitHub repository, it’s always been possible to build a copy of React that includes the latest changes. However it’s much easier for developers to install React from npm, so we occasionally publish prerelease builds to the npm registry. A recent example is the 16.7 alpha, which included an early version of the Hooks API.

We would like to make it even easier for developers to test prerelease builds of React, so we’re formalizing our process with three separate release channels.

Release Channels

The information in this post is also available on our Release Channels page. We will update that document whenever there are changes to our release process.

Each of React’s release channels is designed for a distinct use case:

• Latest is for stable, semver React releases. It’s what you get when you install React from npm. This is the channel you’re already using today. Use this for all user-facing React applications.
• Next tracks the master branch of the React source code repository. Think of these as release candidates for the next minor semver release. Use this for integration testing between React and third party projects.
• Experimental includes experimental APIs and features that aren’t available in the stable releases. These also track the master branch, but with additional feature flags turned on. Use this to try out upcoming features before they are released.

All releases are published to npm, but only Latest uses semantic versioning. Prereleases (those in the Next and Experimental channels) have versions generated from a hash of their contents, e.g. 0.0.0-1022ee0ec for Next and 0.0.0-experimental-1022ee0ec for Experimental.

The only officially supported release channel for user-facing applications is Latest. Next and Experimental releases are provided for testing purposes only, and we provide no guarantees that behavior won’t change between releases. They do not follow the semver protocol that we use for releases from Latest.

By publishing prereleases to the same registry that we use for stable releases, we are able to take advantage of the many tools that support the npm workflow, like unpkg and CodeSandbox.

Latest Channel

Latest is the channel used for stable React releases. It corresponds to the latest tag on npm. It is the recommended channel for all React apps that are shipped to real users.

If you’re not sure which channel you should use, it’s Latest. If you’re a React developer, this is what you’re already using.

You can expect updates to Latest to be extremely stable. Versions follow the semantic versioning scheme. Learn more about our commitment to stability and incremental migration in our versioning policy.

Next Channel

The Next channel is a prerelease channel that tracks the master branch of the React repository. We use prereleases in the Next channel as release candidates for the Latest channel. You can think of Next as a superset of Latest that is updated more frequently.

The degree of change between the most recent Next release and the most recent Latest release is approximately the same as you would find between two minor semver releases. However, the Next channel does not conform to semantic versioning. You should expect occasional breaking changes between successive releases in the Next channel.

Do not use prereleases in user-facing applications.

Releases in Next are published with the next tag on npm. Versions are generated from a hash of the build’s contents, e.g. 0.0.0-1022ee0ec.

Using the Next Channel for Integration Testing

The Next channel is designed to support integration testing between React and other projects.

All changes to React go through extensive internal testing before they are released to the public. However, there are myriad environments and configurations used throughout the React ecosystem, and it’s not possible for us to test against every single one.

If you’re the author of a third party React framework, library, developer tool, or similar infrastructure-type project, you can help us keep React stable for your users and the entire React community by periodically running your test suite against the most recent changes. If you’re interested, follow these steps:

• Set up a cron job using your preferred continuous integration platform. Cron jobs are supported by both CircleCI and Travis CI.

• In the cron job, update your React packages to the most recent React release in the Next channel, using next tag on npm. Using the npm cli:

  npm update react@next react-dom@next

  Or yarn:

  yarn upgrade react@next react-dom@next

• Run your test suite against the updated packages.
• If everything passes, great! You can expect that your project will work with the next minor React release.
• If something breaks unexpectedly, please let us know by filing an issue.

A project that uses this workflow is Next.js. (No pun intended! Seriously!) You can refer to their CircleCI configuration as an example.

Experimental Channel

Like Next, the Experimental channel is a prerelease channel that tracks the master branch of the React repository. Unlike Next, Experimental releases include additional features and APIs that are not ready for wider release.

Usually, an update to Next is accompanied by a corresponding update to Experimental. They are based on the same source revision, but are built using a different set of feature flags.

Experimental releases may be significantly different than releases to Next and Latest. Do not use Experimental releases in user-facing applications. You should expect frequent breaking changes between releases in the Experimental channel.

Releases in Experimental are published with the experimental tag on npm. Versions are generated from a hash of the build’s contents, e.g. 0.0.0-experimental-1022ee0ec.

What Goes Into an Experimental Release?

Experimental features are ones that are not ready to be released to the wider public, and may change drastically before they are finalized. Some experiments may never be finalized — the reason we have experiments is to test the viability of proposed changes.

For example, if the Experimental channel had existed when we announced Hooks, we would have released Hooks to the Experimental channel weeks before they were available in Latest.

You may find it valuable to run integration tests against Experimental. This is up to you. However, be advised that Experimental is even less stable than Next. We do not guarantee any stability between Experimental releases.

How Can I Learn More About Experimental Features?

Experimental features may or may not be documented. Usually, experiments aren’t documented until they are close to shipping in Next or Stable.

If a feature is not documented, they may be accompanied by an RFC.

We will post to the React blog when we’re ready to announce new experiments, but that doesn’t mean we will publicize every experiment.

You can always refer to our public GitHub repository’s history for a comprehensive list of changes.

At React Conf 2019 we announced an experimental release of React that supports Concurrent Mode and Suspense. In this post we’ll introduce best practices for using them that we’ve identified through the process of building the new facebook.com.

This post will be most relevant to people working on data fetching libraries for React.

It shows how to best integrate them with Concurrent Mode and Suspense. The patterns introduced here are based on Relay — our library for building data-driven UIs with GraphQL. However, the ideas in this post apply to other GraphQL clients as well as libraries using REST or other approaches.

This post is aimed at library authors. If you’re primarily an application developer, you might still find some interesting ideas here, but don’t feel like you have to read it in its entirety.

Talk Videos

If you prefer to watch videos, some of the ideas from this blog post have been referenced in several React Conf 2019 presentations:

• Data Fetching with Suspense in Relay by Joe Savona
• Building the New Facebook with React and Relay by Ashley Watkins
• React Conf Keynote by Yuzhi Zheng

This post presents a deeper dive on implementing a data fetching library with Suspense.

Putting User Experience First

The React team and community has long placed a deserved emphasis on developer experience: ensuring that React has good error messages, focusing on components as a way to reason locally about app behavior, crafting APIs that are predictable and encourage correct usage by design, etc. But we haven’t provided enough guidance on the best ways to achieve a great user experience in large apps.

For example, the React team has focused on framework performance and providing tools for developers to debug and tune application performance (e.g. React.memo). But we haven’t been as opinionated about the high-level patterns that make the difference between fast, fluid apps and slow, janky ones. We always want to ensure that React remains approachable to new users and supports a variety of use-cases — not every app has to be “blazing” fast. But as a community we can and should aim high. We should make it as easy as possible to build apps that start fast and stay fast, even as they grow in complexity, for users on varying devices and networks around the world.

Concurrent Mode and Suspense are experimental features that can help developers achieve this goal. We first introduced them at JSConf Iceland in 2018, intentionally sharing details very early to give the community time to digest the new concepts and to set the stage for subsequent changes. Since then we’ve completed related work, such as the new Context API and the introduction of Hooks, which are designed in part to help developers naturally write code that is more compatible with Concurrent Mode. But we didn’t want to implement these features and release them without validating that they work. So over the past year, the React, Relay, web infrastructure, and product teams at Facebook have all collaborated closely to build a new version of facebook.com that deeply integrates Concurrent Mode and Suspense to create an experience with a more fluid and app-like feel.

Thanks to this project, we’re more confident than ever that Concurrent Mode and Suspense can make it easier to deliver great, fast user experiences. But doing so requires rethinking how we approach loading code and data for our apps. Effectively all of the data-fetching on the new facebook.com is powered by Relay Hooks — new Hooks-based Relay APIs that integrate with Concurrent Mode and Suspense out of the box.

Relay Hooks — and GraphQL — won’t be for everyone, and that’s ok! Through our work on these APIs we’ve identified a set of more general patterns for using Suspense. Even if Relay isn’t the right fit for you, we think the key patterns we’ve introduced with Relay Hooks can be adapted to other frameworks.

Best Practices for Suspense

It’s tempting to focus only on the total startup time for an app — but it turns out that users’ perception of performance is determined by more than the absolute loading time. For example, when comparing two apps with the same absolute startup time, our research shows that users will generally perceive the one with fewer intermediate loading states and fewer layout changes as having loaded faster. Suspense is a powerful tool for carefully orchestrating an elegant loading sequence with a few, well-defined states that progressively reveal content. But improving perceived performance only goes so far — our apps still shouldn’t take forever to fetch all of their code, data, images, and other assets.

The traditional approach to loading data in React apps involves what we refer to as “fetch-on-render”. First we render a component with a spinner, then fetch data on mount (componentDidMount or useEffect), and finally update to render the resulting data. It’s certainly possible to use this pattern with Suspense: instead of initially rendering a placeholder itself, a component can “suspend” — indicate to React that it isn’t ready yet. This will tell React to find the nearest ancestor <Suspense fallback={<Placeholder/>}>, and render its fallback instead. If you watched earlier Suspense demos this example may feel familiar — it’s how we originally imagined using Suspense for data-fetching.

It turns out that this approach has some limitations. Consider a page that shows a social media post by a user, along with comments on that post. That might be structured as a <Post> component that renders both the post body and a <CommentList> to show the comments. Using the fetch-on-render approach described above to implement this could cause sequential round trips (sometimes referred to as a “waterfall”). First the data for the <Post> component would be fetched and then the data for <CommentList> would be fetched, increasing the time it takes to show the full page.

There’s also another often-overlooked downside to this approach. If <Post> eagerly requires (or imports) the <CommentList> component, our app will have to wait to show the post body while the code for the comments is downloading. We could lazily load <CommentList>, but then that would delay fetching comments data and increase the time to show the full page. How do we resolve this problem without compromising on the user experience?

Render As You Fetch

The fetch-on-render approach is widely used by React apps today and can certainly be used to create great apps. But can we do even better? Let’s step back and consider our goal.

In the above <Post> example, we’d ideally show the more important content — the post body — as early as possible, without negatively impacting the time to show the full page (including comments). Let’s consider the key constraints on any solution and look at how we can achieve them:

• Showing the more important content (the post body) as early as possible means that we need to load the code and data for the view incrementally. We don’t want to block showing the post body on the code for <CommentList> being downloaded, for example.
• At the same time we don’t want to increase the time to show the full page including comments. So we need to start loading the code and data for the comments as soon as possible, ideally in parallel with loading the post body.

This might sound difficult to achieve — but these constraints are actually incredibly helpful. They rule out a large number of approaches and spell out a solution for us. This brings us to the key patterns we’ve implemented in Relay Hooks, and that can be adapted to other data-fetching libraries. We’ll look at each one in turn and then see how they add up to achieve our goal of fast, delightful loading experiences:

1. Parallel data and view trees
2. Fetch in event handlers
3. Load data incrementally
4. Treat code like data

Parallel Data and View Trees

One of the most appealing things about the fetch-on-render pattern is that it colocates what data a component needs with how to render that data. This colocation is great — an example of how it makes sense to group code by concerns and not by technologies. All the issues we saw above were due to when we fetch data in this approach: upon rendering. We need to be able to fetch data before we’ve rendered the component. The only way to achieve that is by extracting the data dependencies into parallel data and view trees.

Here’s how that works in Relay Hooks. Continuing our example of a social media post with body and comments, here’s how we might define it with Relay Hooks:

// Post.js
function Post(props) {
  // Given a reference to some post - `props.post` - *what* data
  // do we need about that post?
  const postData = useFragment(graphql`
    fragment PostData on Post @refetchable(queryName: "PostQuery") {
      author
      title
      # ...  more fields ...
    }
  `, props.post);

  // Now that we have the data, how do we render it?
  return (
    <div>
      <h1>{postData.title}</h1>
      <h2>by {postData.author}</h2>
      {/* more fields  */}
    </div>
  );
}

Although the GraphQL is written within the component, Relay has a build step (Relay Compiler) that extracts these data-dependencies into separate files and aggregates the GraphQL for each view into a single query. So we get the benefit of colocating concerns, while at runtime having parallel data and view trees. Other frameworks could achieve a similar effect by allowing developers to define data-fetching logic in a sibling file (maybe Post.data.js), or perhaps integrate with a bundler to allow defining data dependencies with UI code and automatically extracting it, similar to Relay Compiler.

The key is that regardless of the technology we’re using to load our data — GraphQL, REST, etc — we can separate what data to load from how and when to actually load it. But once we do that, how and when do we fetch our data?

Fetch in Event Handlers

Imagine that we’re about to navigate from a list of a user’s posts to the page for a specific post. We’ll need to download the code for that page — Post.js — and also fetch its data.

Waiting until we render the component has problems as we saw above. The key is to start fetching code and data for a new view in the same event handler that triggers showing that view. We can either fetch the data within our router — if our router supports preloading data for routes — or in the click event on the link that triggered the navigation. It turns out that the React Router folks are already hard at work on building APIs to support preloading data for routes. But other routing frameworks can implement this idea too.

Conceptually, we want every route definition to include two things: what component to render and what data to preload, as a function of the route/url params. Here’s what such a route definition might look like. This example is loosely inspired by React Router’s route definitions and is primarily intended to demonstrate the concept, not a specific API:

// PostRoute.js (GraphQL version)

// Relay generated query for loading Post data
import PostQuery from './__generated__/PostQuery.graphql';

const PostRoute = {
  // a matching expression for which paths to handle
  path: '/post/:id',

  // what component to render for this route
  component: React.lazy(() => import('./Post')),

  // data to load for this route, as function of the route
  // parameters
  prepare: routeParams => {
    // Relay extracts queries from components, allowing us to reference
    // the data dependencies -- data tree -- from outside.
    const postData = preloadQuery(PostQuery, {
      postId: routeParams.id,
    });

    return { postData };
  },
};

export default PostRoute;

Given such a definition, a router can:

• Match a URL to a route definition.
• Call the prepare() function to start loading that route’s data. Note that prepare() is synchronous — we don’t wait for the data to be ready, since we want to start rendering more important parts of the view (like the post body) as quickly as possible.
• Pass the preloaded data to the component. If the component is ready — the React.lazy dynamic import has completed — the component will render and try to access its data. If not, React.lazy will suspend until the code is ready.

This approach can be generalized to other data-fetching solutions. An app that uses REST might define a route like this:

// PostRoute.js (REST version)

// Manually written logic for loading the data for the component
import PostData from './Post.data';

const PostRoute = {
  // a matching expression for which paths to handle
  path: '/post/:id',

  // what component to render for this route
  component: React.lazy(() => import('./Post')),

  // data to load for this route, as function of the route
  // parameters
  prepare: routeParams => {
    const postData = preloadRestEndpoint(
      PostData.endpointUrl, 
      {
        postId: routeParams.id,
      },
    );
    return { postData };
  },
};

export default PostRoute;

This same approach can be employed not just for routing, but in other places where we show content lazily or based on user interaction. For example, a tab component could eagerly load the first tab’s code and data, and then use the same pattern as above to load the code and data for other tabs in the tab-change event handler. A component that displays a modal could preload the code and data for the modal in the click handler that triggers opening the modal, and so on.

Once we’ve implemented the ability to start loading code and data for a view independently, we have the option to go one step further. Consider a <Link to={path} /> component that links to a route. If the user hovers over that link, there’s a reasonable chance they’ll click it. And if they press the mouse down, there’s an even better chance that they’ll complete the click. If we can load code and data for a view after the user clicks, we can also start that work before they click, getting a head start on preparing the view.

Best of all, we can centralize that logic in a few key places — a router or core UI components — and get any performance benefits automatically throughout our app. Of course preloading isn’t always beneficial. It’s something an application would tune based on the user’s device or network speed to avoid eating up user’s data plans. But the pattern here makes it easier to centralize the implementation of preloading and the decision of whether to enable it or not.

Load Data Incrementally

The above patterns — parallel data/view trees and fetching in event handlers — let us start loading all the data for a view earlier. But we still want to be able to show more important parts of the view without waiting for all of our data. At Facebook we’ve implemented support for this in GraphQL and Relay in the form of some new GraphQL directives (annotations that affect how/when data is delivered, but not what data). These new directives, called @defer and @stream, allow us to retrieve data incrementally. For example, consider our <Post> component from above. We want to show the body without waiting for the comments to be ready. We can achieve this with @defer and <Suspense>:

// Post.js
function Post(props) {
  const postData = useFragment(graphql`
    fragment PostData on Post {
      author
      title

      # fetch data for the comments, but don't block on it being ready
      ...CommentList @defer
    }
  `, props.post);

  return (
    <div>
      <h1>{postData.title}</h1>
      <h2>by {postData.author}</h2>
      {/* @defer pairs naturally with <Suspense> to make the UI non-blocking too */}
      <Suspense fallback={<Spinner/>}>
        <CommentList post={postData} />
      </Suspense>
    </div>
  );
}

Here, our GraphQL server will stream back the results, first returning the author and title fields and then returning the comment data when it’s ready. We wrap <CommentList> in a <Suspense> boundary so that we can render the post body before <CommentList> and its data are ready. This same pattern can be applied to other frameworks as well. For example, apps that call a REST API might make parallel requests to fetch the body and comments data for a post to avoid blocking on all the data being ready.

Treat Code Like Data

But there’s one thing that’s still missing. We’ve shown how to preload data for a route — but what about code? The example above cheated a bit and used React.lazy. However, React.lazy is, as the name implies, lazy. It won’t start downloading code until the lazy component is actually rendered — it’s “fetch-on-render” for code!

To solve this, the React team is considering APIs that would allow bundle splitting and eager preloading for code as well. That would allow a user to pass some form of lazy component to a router, and for the router to trigger loading the code alongside its data as early as possible.

Putting It All Together

To recap, achieving a great loading experience means that we need to start loading code and data as early as possible, but without waiting for all of it to be ready. Parallel data and view trees allow us to load the data for a view in parallel with loading the view (code) itself. Fetching in an event handler means we can start loading data as early as possible, and even optimistically preload a view when we have enough confidence that a user will navigate to it. Loading data incrementally allows us to load important data earlier without delaying the fetching of less important data. And treating code as data — and preloading it with similar APIs — allows us to load it earlier too.

Using These Patterns

These patterns aren’t just ideas — we’ve implemented them in Relay Hooks and are using them in production throughout the new facebook.com (which is currently in beta testing). If you’re interested in using or learning more about these patterns, here are some resources:

• The React Concurrent docs explore how to use Concurrent Mode and Suspense and go into more detail about many of these patterns. It’s a great resource to learn more about the APIs and use-cases they support.
• The experimental release of Relay Hooks implements the patterns described here.

• We’ve implemented two similar example apps that demonstrate these concepts:

  • The Relay Hooks example app uses GitHub’s public GraphQL API to implement a simple issue tracker app. It includes nested route support with code and data preloading. The code is fully commented — we encourage cloning the repo, running the app locally, and exploring how it works.
  • We also have a non-GraphQL version of the app that demonstrates how these concepts can be applied to other data-fetching libraries.

While the APIs around Concurrent Mode and Suspense are still experimental, we’re confident that the ideas in this post are proven by practice. However, we understand that Relay and GraphQL aren’t the right fit for everyone. That’s ok! We’re actively exploring how to generalize these patterns to approaches such as REST, and are exploring ideas for a more generic (ie non-GraphQL) API for composing a tree of data dependencies. In the meantime, we’re excited to see what new libraries will emerge that implement the patterns described in this post to make it easier to build great, fast user experiences.

Joe Allington was persuaded to dance on TikTok for the first time in January. Now he's got 1.5 million followers.

São Paulo Governor João Doria has imposed tough virus curbs, a move slammed by President Bolsonaro.

D3 is great at data visualizations, but it manipulates the DOM directly to display that data. Rendering DOM elements is where React shines. It uses a virtual representation of the DOM (virtual DOM) and a super performant diffing algorithm in order to determine the fastest way to update the DOM. We want to leverage React’s highly efficient, declarative, and reusable components with D3’s data utility functions.

At this point, we can safely say that React is the preferred JavaScript library for building user interfaces. It is used practically everywhere and is almost as pervasive as jQuery. It has an API that is simple, powerful, and easy to learn. Its performance metrics are really impressive thanks to the Virtual DOM and its clever diff algorithm between state changes. Nothing, however, is perfect, and React too has its limitations. One of React’s greatest strengths is the ease with which it integrate third-party libraries, but some libraries, especially opinionated ones, are more difficult to integrate than others.

An extremely popular library that can be tricky to integrate with React is D3.js. D3 is an excellent data visualization library with a rich and powerful API. It is the gold standard of data visualizations. However, Because this library is opinionated about data, it is no trivial endeavour to get it to work with React. A few simple strategies permit these two libraries to work together in very powerful ways.

Editor’s Note: Check out our upcoming workshop, React and D3, a crash course in learning how to create data visualizations with these two in demand libraries. Reserve your spot now on Eventbrite and get 20% off admission. Learn more at the Eventbrite page

What is React?

React is an open-source JavaScript library for creating user interfaces that addresses the challenges of building large applications with data that changes over time. Originally developed at Facebook, it is now seen in many of the most commonly used web applications including Instagram, Netflix, Airbnb, and HelloSign.

Why is React so popular?

React helps developers build applications by helping manage the application state. It’s simple, declarative, and composable. React is not a traditional MVC framework because React is really only interested in building user interfaces. Some have called it the “V(iew)” in MVC, but that’s a little misleading. React’s viewpoint is different. As application logic has reoriented toward the client, developers have applied more structure to their front-end JavaScript. We applied a paradigm that we already understood from the server (MVC) to the browser. Of course, the browser environment is very different from the server. React acknowledges that client-side applications are really a collection of UI components that should react to events like user interaction.

React encourages the building applications out of self-contained, reusable components that only care about a small piece of the UI. Other frameworks such as Angular also attempt to do this, but React stands out because it enforces a unidirectional data flow from parent component to child component. This makes debugging much easier. Debugging is the hardest part of application development, so while React is more verbose that other libraries or frameworks, in the end it saves a lot of time. In a framework like Angular’s, it can be hard to figure out where a bug is coming from: The view? The model? The controller? The directive? The directive controller? Data in Angular flows in many different directions, and this makes it hard to reason about that state of your application. In React, when there is a bug (and there will be!), you can quickly determine where the bug originated from because data only moves in one direction. Locating a bug is as simple as connecting the numbered dots until you find the culprit.

What is D3?

D3 (Data-Driven Documents) is a JavaScript library for producing dynamic, interactive data-visualizations. It’s fairly low level, and the developer has a lot of control over the end result. It takes a bit of work to get D3 to do what you want, so if you’re looking for a more prepackaged solution, you’re probably better off with highcharts.js. That said, it is fairly simple to pick up once you get the hang of it.

D3 does four main things:

1. LOADS: D3 has convenient methods for importing data from CSV documents.
2. BINDS: D3 binds data elements to the DOM via JavaScript and SVG.
3. TRANSFORMS: data can be adjusted to fit your visual requirements
4. TRANSITIONS: D3 can respond to user input and animate elements based on that input

Why Would We Want To Use React with D3?

D3 is great at data visualizations, but it manipulates the DOM directly to display that data. Rendering DOM elements is where React shines. It uses a virtual representation of the DOM (virtual DOM) and a super performant diffing algorithm in order to determine the fastest way to update the DOM. We want to leverage React’s highly efficient, declarative, and reusable components with D3’s data utility functions. Also, once we create a chart component, we can want to be able to reuse that chart with different data anywhere in our app.

How to use React and D3?

D3, like React, is declarative.D3 uses data binding, whereas React uses a unidirectional data flow paradigm. Getting these two libraries to work together takes a bit of work, but the strategy is fairly simple: since SVG lives in the DOM, let React handle displaying SVG representations of the data and lett D3 handle all the math to render the data.

Of course, we’ll have to make compromises. React is unopinionated and flexible, thereby allowing you to accomplish whatever needs to be done. Some tasks, like creating axes, are tedious. We can let D3 directly access the DOM and create. It handles axes well, and since we only need to create very few, this tactic won’t affect performance.

Let’s go through a simple example. I created a repository you can use to follow along here: playing-with-react-and-d3. You can follow in the unfinished directory and if you get stuck you can take a look at the finished directory.

Let’s generate a random list of X-Y coordinates and display them on a ScatterPlot chart. If you’re following the tutorial, a finished example is provided for you under the “finished” directory, but you can also follow along under “unfinished.” I’ve gone through the trouble of doing all the setup for you. The build will automatically be created from “unfinished/src/index.jsx”

Let’s start by creating a simple “Hello World!” React component. Create a file under “components” named “chart.jsx”

// unfinished/src/components/chart.jsx
import React from 'react';

export default (props) => {
  return <h1>Hello, World!</h1>;
}

This example is simple, but let’s go over the explanation anyway. Since we’re rendering a simple H1 with no state, we can just export a function that returns the HTML we expect. If you’re familiar with Angular or Ember, it might look weird to insert HTML directly into our JS code. On the one hand, this goes against everything we’ve learned about unobtrusive JavaScript. But on the other hand, it actually makes sense: we’re not putting JavaScript in our HTML, we’re putting our HTML into our JavaScript. React sees HTML and client-side JavaScript as fundamentally bonded together. They’re both concerned about one thing – rendering UI components to the user. They simply cannot be separated without losing the ability to see what your component is going at a glance. The great benefits of this approach is that you can describe exactly what your component will look like when it’s rendered.

Also, keep in mind that this is only possible with JSX, which translates HTML elements into React functions that will render the HTML to the page.

Now, let’s move on and mount our component to the DOM. Open up “index.jsx”

// unfinished/src/index.jsx
import './main.css';
import React    from 'react';
import ReactDOM from 'react-dom';
import Chart    from './components/chart.jsx';

const mountingPoint = document.createElement('div');
mountingPoint.className = 'react-app';
document.body.appendChild(mountingPoint);
ReactDOM.render(<Chart/>, mountingPoint);

You probably noticed a few things. You might be wondering why we’re requiring a CSS file. We’re using Webpack, which allows us to require CSS files. This is very useful when we modularize both our stylesheets and our JavaScript. We’re also creating a div in which we want to mount our React app. This is just a good practice in case you want to do other things on the page then render a React component. Lastly, we’re calling render on ReactDOM with 2 arguments, the name of the component and the DOM element we want to mount it on.

Now, let’s install all the dependencies by navigating to the unfinished directory and running npm i. Then, fire up the server with npm run start and go to localhost:8080

Awesome! We have rendered our first React component! Let’s do something a little less trivial now.

Let’s compose some functions that will create an array of random data points and then render a scatter plot. While we’re at it, we’ll add a button to randomize the dataset and trigger a re-render of our app. Let’s open up our Chart component and add the following:

// unfinished/src/components/chart.jsx
import React       from 'react';
import ScatterPlot from './scatter-plot';

const styles = {
  width   : 500,
  height  : 300,
  padding : 30,
};

// The number of data points for the chart.
const numDataPoints = 50;

// A function that returns a random number from 0 to 1000
const randomNum     = () => Math.floor(Math.random() * 1000);

// A function that creates an array of 50 elements of (x, y) coordinates.
const randomDataSet = () => {
  return Array.apply(null, {length: numDataPoints}).map(() => [randomNum(), randomNum()]);
}

export default class Chart extends React.Component{
  constructor(props) {
    super(props);
    this.state = { data: randomDataSet() };
  }

  randomizeData() {
    this.setState({ data: randomDataSet() });
  }

  render() {
    return <div>
      <h1>Playing With React and D3</h1>
      <ScatterPlot {...this.state} {...styles} />
      <div className="controls">
        <button className="btn randomize" onClick={() => this.randomizeData()}>
          Randomize Data
        </button>
      </div>
    </div>
  }
}

Since we want our component to manage it’s own state, we need to add a bit more code than was necessary for our previous “Hello World” stateless functional component. Instead of just a function, we’re going to extend React.Component and describe our component in the render() method. render() is the heart of any React component. It describes what our component is supposed to looks like. React will call render() on initial mount and on every state change.

Inside of render(), we are both rendering a scatter plot component as if it were an HTML element and setting some properties or “props”. The ... syntax is a convenient JSX and ES2015 spread operator that spreads the attributes of an array or object instead of doing all of that explicitly. For more information check out: JSX Spread Attributes. We’re going to use render() to pass our data and a style object that will be used by some of our child components.

In addition, we’re also rendering a button with an onClick event handler. We’re going to wrap this.randomizeData() with an arrow function and bind the value of this to our Chart component. When the button is clicked, randomizeData() will call this.setState() and pass in some new data.

Let’s talk about this.setState(). If render() is the heart of a React component, setState() is the brains of a component. setState explicitly tells React that we’re changing the state, thereby triggering a re-render of the component and its children. This essentially turns UI components into state machines.

Inside of setState(), we’re passing an object with data set to the randomDataSet(). This means that if we want to retrieve the state of our application, we need only call this.state.whateverStateWereLookingFor. In this case, we can retrieve the randomData by calling this.state.data.

A little side note on how React works: React offers great performance for rendering UI components by implementing a diff algorithm and comparing a virtual DOM in memory with the actual DOM. When you think about it, the DOM is really a large tree structure. If there’s one thing we have learned from decades of computer science research, it’s how to compare and manipulate trees. React takes advantage of clever tree diffing algorithms, but in order to work, each component can only render one parent element (i.e., you cannot render sibling elements). That’s why In the render function we’re wrapping all our elements in one parent div.

Let’s get started with the scatter plot component. Create a file unfinished/src/components/scatter-plot.jsx :

// unfinished/src/components/scatter-plot.jsx
import React        from 'react';
import d3           from 'd3';
import DataCircles  from './data-circles';

// Returns the largest X coordinate from the data set
const xMax   = (data)  => d3.max(data, (d) => d[0]);

// Returns the highest Y coordinate from the data set
const yMax   = (data)  => d3.max(data, (d) => d[1]);

// Returns a function that "scales" X coordinates from the data to fit the chart
const xScale = (props) => {
  return d3.scale.linear()
    .domain([0, xMax(props.data)])
    .range([props.padding, props.width - props.padding * 2]);
};

// Returns a function that "scales" Y coordinates from the data to fit the chart
const yScale = (props) => {
  return d3.scale.linear()
    .domain([0, yMax(props.data)])
    .range([props.height - props.padding, props.padding]);
};

export default (props) => {
  const scales = { xScale: xScale(props), yScale: yScale(props) };
  return <svg width={props.width} height={props.height}>
    <DataCircles {...props} {...scales} />
  </svg>
}

There’s a lot going on here, so let’s start with the stateless functional component that we’re exporting. D3 uses SVG to render data visualizations. D3 has special methods for creating SVG elements and binding data to those elements – but we’re going to let React handle that. We’re creating an SVG element with the properties passed in by the Chart component and which can be accessed via this.props. Then we’re creating a DataCircles component (more on that below) which will render the points for the scatter plot.

Let’s talk about D3 scales. This is where D3 shines. Scales takes care of the messy math involved in converting your data into a format that can be displayed on a chart. If you have a data point value 189281, but your chart is only 200 pixels wide, then D3 scales converts that value to a number you can use.

d3.scale.linear() returns a linear scale. D3 also supports other types of scales (ordinal, logarithmic, square root, etc.), but we won’t be talking about those here. domain is short for an “input domain”, i.e., the range of possible input values. It takes an array of the smallest input value possible and the maximum input value. range on its own is the range of possible output values. So in domain, we’re setting the range of possible data values from our random data, and in range we’re telling D3 the range of our chart. d3.max is a D3 method for determining the maximum value of a dataset. It can take a function which D3 will use to give the max values of the X and Y coordinates.

We use the scales to render the data circles and our axes.

Let’s create the DataCircles component under unfinished/src/components/data-circles.jsx

// unfinished/src/components/data-circles.jsx
import React from 'react';

const renderCircles = (props) => {
  return (coords, index) => {
    const circleProps = {
      cx: props.xScale(coords[0]),
      cy: props.yScale(coords[1]),
      r: 2,
      key: index
    };
    return <circle {...circleProps} />;
  };
};

export default (props) => {
  return <g>{ props.data.map(renderCircles(props)) }</g>
}

In this component, we’re rendering a g element, the SVG equivalent to a div. Since we want to render a point for every set of X-Y coordinates, were must render multiple sibling elements which we wrap together in a g element for React to work. Inside of g, we’re mapping over the data and rendering a circle for each one using renderCircles. renderCircles creates an SVG circle element with a number of properties. Here’s where we’re setting the x and y coordinates (cx and cy respectively) with the D3 scales passed in from the scatter plot component. r is the radius of our circle, and key is something React requires us to do. Since we’re rendering identical sibling components, React’s diffing algorithm needs a way to keep track of them as it updates the DOM over and over. You can use any key you like, as long as it’s unique to the list. Here we’re just going to use the index of each element.

Now, when we look at our browser, we see this:

We can see our random data and randomize that data via user input. Awesome! But we’re missing a way to read this data. What we need are axes. Let’s create them now.

Let’s open up ScatterPlot.jsx and add an XYAxis component

// unfinished/src/components/scatter-plot.jsx

// ...

import XYAxis       from './x-y-axis';

// ...

export default (props) => {
  const scales = { xScale: xScale(props), yScale: yScale(props) };
  return <svg width={props.width} height={props.height}>
    <DataCircles {...props} {...scales} />
    <XYAxis {...props} {...scales} />
  </svg>
}

Now, let’s create the XYAxis component;

// unfinished/src/components/x-y-axis.jsx
import React  from 'react';
import Axis   from './axis';

export default (props) => {
  const xSettings = {
    translate: `translate(0, ${props.height - props.padding})`,
    scale: props.xScale,
    orient: 'bottom'
  };
  const ySettings = {
    translate: `translate(${props.padding}, 0)`,
    scale: props.yScale,
    orient: 'left'
  };
  return <g className="xy-axis">
    <Axis {...xSettings}/>
    <Axis {...ySettings}/>
  </g>
}

For simplicity’s sake, we’re creating two objects which will hold the props for each of our X-Y axes. Let’s create an axis component to explain what these props do. Go ahead and create axis.jsx

// unfinished/src/components/x-y-axis.jsx
import React from 'react';
import d3    from 'd3';

export default class Axis extends React.Component {
  componentDidMount() {
    this.renderAxis();
  }

  componentDidUpdate() {
    this.renderAxis();
  }

  renderAxis() {
    var node  = this.refs.axis;
    var axis = d3.svg.axis().orient(this.props.orient).ticks(5).scale(this.props.scale);
    d3.select(node).call(axis);
  }

  render() {
    return <g className="axis" ref="axis" transform={this.props.translate}></g>
  }
}

Our strategy up to this point has been to let React exclusively handle the DOM. This is a good general rule, but we should leave room for nuance. In this case, the math and work necessary in order to render an axis is quite complicated and D3 has abstracted that pretty nicely. We’re going to let D3 have access to the DOM in this case. And since we’re only going to render a ma

Jake Murzy has been hard at work creating a new navigational library for React Native over the last couple of months. While React JS has the benefit of the highly-regarded React Router, such a comprehensive routing solution doesn’t exist yet in the React Native community. In fact, React Native’s routing landscape has been in constant upheaval for the last year. The library itself has official three ‘navigators’ for handling decision making on which components to show the user, including ‘NavigatorIOS’, ‘Navigator’, and - more recently - ‘NavigatorExperimental’. The open source community likewise has the packages ‘React Native Router Flux’, ‘React Native Router Native’, and ‘React Native Redux Router’, which of which are in various states of completion, or, more commonly, disrepair.

Jake Murzy has been hard at work creating a new navigational library for React Native over the last couple of months. While React JS has the benefit of the highly-regarded React Router, such a comprehensive routing solution doesn’t exist yet in the React Native community. In fact, React Native’s routing landscape has been in constant upheaval for the last year. The library itself has official three ‘navigators’ for handling decision making on which components to show the user, including ‘NavigatorIOS’, ‘Navigator’, and - more recently - ‘NavigatorExperimental’. The open source community likewise has the packages ‘React Native Router Flux’, ‘React Native Router Native’, and ‘React Native Redux Router’, which of which are in various states of completion, or, more commonly, disrepair.

React Router Native appears to focus on matching the API of the immensely popular React Router package, even going as far as introducing the concept of a URL into React Native, which bucks the notion that only web applications need or deserve a URL.

Today Jake is going to share some of his thoughts about his new library.

Q: Hi Jake! The React Native library contains several navigation solutions and the surrounding ecosystem has multiple routing libraries. What made you decide to make your own?

Hey! Thanks for reaching out. I’ve been eagerly watching what’s happening with navigation on React Native for a while. Until very recently, the whole Navigation scene in React Native was a mess. Navigator was being deprecated in favor of NavigationExperimental and NavigationExperimental wasn’t ready for prime time.

My team was just starting a new project so I tried quite a few of the available solutions. Having successfully used React Router on the web, we were looking for a similar solution. Unfortunately, React Router did not support React Native, and other solutions we found were either very unstable, had a hard time keeping up with upstream changes on each release or the quality of code was quite poor.

NavigationExperimental did most of what we wanted but it was a bit too low level so often times we found ourselves writing navigation related code and you can imagine how this gets tedious fast. The low level nature of NavigationExperimental is really by design to allow abstractions to be built up in higher layers. So to finally answer your question, the project came directly out of my frustration trying to make navigation work on React Native as good as React Router did on the web.

Q: What is the strength of your routing system? Is there any type of app that would be a perfect fit with React Router Native? Conversely, is there any type of app that wouldn’t be a good fit with the library?

The use cases for React Router Native is pretty much the same as NavigationExperimental—which is the only supported navigation library by the React Native team. React Router Native is a very thin layer on top of NavigationExperimental that offers React Router’s mental model in a native app. Under the hood, it uses React Router for routing and NavigationExperimental for rendering user components. This is a very powerful combination that makes URLs possible on mobile.

Most apps do not have deep-linking capabilities because implementing it for each screen in your app is a challenging task. Even within apps, users are often forced to take screenshots to share information. And for many, it’s vital that their apps support deep-linking. For example, Yelp goes as far to show a share prompt when users take screenshots of business listings. React Router Native enables developers to implement deep-linking in their apps without putting forth much effort. This can pave the way for a more connected app ecosystem.

That being said, we’re still in the early days of React Native figuring out the right abstractions. Navigation on mobile is a challenging task, and having different flavors is only healthier as the community weighs the pros and cons of each approach rather than second guessing best-practices. So I’m hoping to get the community involved to shape the direction of the project.

Q: Is React Router Native designed to be used with any of the official Navigation components written by the React Native team?

Absolutely. One of the primary goals of the project is that we follow React’s “learn once, write anywhere” principle. So you can use the community maintained components, interpolators and pan responders from React Native, and everything is highly customizable if you need instruct NavigationExperimental to do fancy transition animations, etc.

Q: The React Router team has somewhat famously rewritten their API several times in the last two years, each time introducing several breaking changes. Do you hope to keep your library at parity with React Router, breaking changes and all? Case in point, the V4 release of React Router will introduce an all-new API.

React Router v4 is a complete rewrite. There was a lot of head-scratching on Twitter over the entire new set of breaking changes. Many people thought v4 should at best have been released under a different name. I’m not sure if I agree with that sentiment though, I understand where it is coming from. React Router v4 is a preview release, and in my opinion, it’s really hard to argue against replacing a foreign API with simple React components. I do hope to keep the library at parity with React Router, and to be honest, v4’s new everything-is-a-component approach makes the integration even easier. So over the next few weeks I’ll be working on v4 support.

Q: If you were new to React Native, which routing solution would you use? Why?

This is a hard one to answer. Eric Vicenti has done a great job on NavigationExperimental and most of the issues have been sorted out by the community over the last few months. So if you’re familiar with Redux concepts and comfortable writing your own reducers to manage navigation state, NavigationExperimental is a great choice.

One that I’m surprised you didn’t mention that deserves more attention is ExNavigation—another fairly new addition to the brewery. It also uses NavigationExperimental and is maintained by Adam Miskiewicz, Brent Vatne and other awesome members of the Exponent community. It feels a bit tied to the Exponent platform, but runs perfectly fine on React Native and is open source. So you’ve got that.

Finally, If you’re just getting started with React Native and all you need is to be able to click a button and have it transition to a different scene but you don’t want it to get in your way when you need to reach in and apply complex navigational patterns, I strongly recommend you take React Router Native for a spin.

React Native continues on a development spree in late 2016. With an ambitious two-week release cycle, the framework makes rapid progress towards feature and performance parity with its native Android and iOS equivalents. At the same time, these quick release periods frequently introduce breaking changes, difficulty with setup, and challenges with basic configuration.

Enter Exponent, a tool that promises easier setup, development, and deployment of React Native applications. Rather than being a replacement for React Native, as it is sometimes confused, Exponent augments React Native by dramatically simplifying the development and deployment processes. Whereas basic setup with an Android environment to develop with React Native can take over an hour by hand, even for experienced engineers, Exponent shortens the time to start to “Hello World” to a handful of minutes.

React Native continues on a development spree in late 2016. With an ambitious two-week release cycle, the framework makes rapid progress towards feature and performance parity with its native Android and iOS equivalents. At the same time, these quick release periods frequently introduce breaking changes, difficulty with setup, and challenges with basic configuration.

Enter Exponent, a tool that promises easier setup, development, and deployment of React Native applications. Rather than being a replacement for React Native, as it is sometimes confused, Exponent augments React Native by dramatically simplifying the development and deployment processes. Whereas basic setup with an Android environment to develop with React Native can take over an hour by hand, even for experienced engineers, Exponent shortens the time to start to “Hello World” to a handful of minutes.

Exponent’s prime feature is revealed as it’s namesake IDE. The Exponent IDE is development platform for not only developing apps to test in their respective environment simulators, but also simplifies testing them on real devices.

One of the cofounders of Exponent, Charlie Cheever, agreed to answer a few questions about Exponent and its purpose in the community.

Hi, Charlie. Congrats on the release of Exponent! One of the toughest aspects of Exponent is understanding what its purpose is. What is the primary goal of Exponent?

Thanks :)

Before I worked on mobile software, I spent about 15 years making websites. When I started working on the Quora iPhone app and Android app, it felt like time traveling back to 1993. So many things to worry about that have nothing to do with the product you want to build.

One thing we’re trying to do with Exponent is making it as easy to develop native mobile apps as it is to make websites, or even easier! I think about how I learned to build software as a kid–making games on my TI-85 and making Hypercard stacks–and I want to make it so that the middle school kids of today can make cool stuff for themselves and their friends.

Basic environment setup of the iOS and Android simulators for developing React Native apps is commonly cited as a headache by new developers. What does Exponent do to alleviate this pain?

The biggest thing that Exponent does is take care of everything related to native code for you. So you don’t need to know Swift/Obj-C/Java or even have Xcode or Android Studio to be able to write React Native apps. You write just JavaScript and Exponent has everything else already setup for you.

Since you don’t write any native code with Exponent, just JavaScript, Exponent has a lot of the most popular native modules built in. Native maps, push notifications, Facebook and Google login, camera and camera roll access, contacts, TouchID, and a native video player are all included among other things. We’re always adding more of these as well. We just added full OpenGL support last week and did a game jam and made some mini games with it and are adding sound soon.

We sometimes talk about Exponent as being like Rails for React Native. You could write a website in Ruby on your own. but Rails sets up a bunch of sensible things right off that bat that work together in a coherent way and we kind of do the same thing for React Native. Exponent includes instant app updating as a default, so you can deploy new code and assets with one command in seconds, even faster than most websites can be deployed.

Even after getting set up with the Android and iOS simulators, testing a React Native app on a real phone can still be a challenge. How does Exponent make it easier to share apps in progress with would-be users?

You can actually open any Exponent project that you’re working on in our development app right away. When you develop with Exponent, you get a URL for your project, and you can open that URL on any phone with the Exponent developer app which you can download from the iOS App Store or Google Play Store. You don’t need to jack your phone into your computer–just open the URL.

Another really cool thing about this is that, if you’re working with someone else, you can just send them the URL and they can open it on their phone as well, even if they are halfway around the world.

We’ve done a bunch of work to make this pretty nice, like having console.log work even if the phone running your code isn’t plugged into your computer. And you can, of course, open your project on the iOS Simulator or an Android Emulator as well if you prefer.

I know you mentioned a lot of people have trouble getting React Native setup on Android especially. With Exponent, every project works on both iOS and Android from the start and you never have to deal with Android Studio, so the process of getting going is much easier.

What type, or genre, of application would be a good fit with React Native and Exponent?

I would actually use React Native for almost any mobile app at this point. Doing development the traditional way (writing Swift/Java/Obj-C code) is just too hard to iterate on when you consider the slowness of the code-compile-copy-run loop and the fact that you have to write your app twice (and then keep it in sync!). The other thing that is an absolutely huge deal here but is sometimes overlooked is the layout engine. It’s much easier to build and change a layout in React Native’s Flexbox than any of the UI libraries that I’ve seen for Java/Swift/Obj-C.

And if you need to do something really intense, like Snapchat live video filters, you can just write your own code as a native module and write the rest of your app in JS.

I would use Exponent for anything I could because it just saves a lot of time and headaches since you don’t need to deal with Android Studio or Xcode. Some people don’t know that you can turn an Exponent project into an app store app for iOS or for Android with just one command.

In general, Exponent will work for you in pretty much every case where just having a mobile website is one of the things that you’re considering. The features are pretty equivalent except that Exponent apps feel like native apps and mobile apps still feel like mobile web apps.

The main reason not to use Exponent is if you have some custom native code that you need that isn’t included with Exponent. The most common reasons that people can’t use Exponent are if they need use Bluetooth or HealthKit or something else low level that isn’t built in to Exponent; or if they need to integrate into an existing project (though we are working right now on a solution that will let you do this).

The exception to all this is games. If you are making a mobile game, Unity is probably the best choice for you. But we did add OpenGL support to Exponent recently and had a game jam and I was surprised at how good some of the entries were, so I think that might change.

TL;DR: For apps that aren’t games, always use React Native (if you need to do something super custom, just do it as a native module). If you can, use Exponent (you can most of the time but check our docs to make sure we’re not missing anything you need).

One aspect of React Native that seems to be undergoing constant flux is its solution for navigation. Between the built in Navigators and open source solutions, do you have any thoughts on an ideal solution for navigation?

Short version: I think you should use Ex-Navigation that Adam Miskiewicz (skevy) and Brent Vatne on our team wrote. Skevy in particular has been thinking about navigation in mobile apps and React Native for a long time. Using Ex-Navigation is definitely a better idea than Navigator or NavigatorIOS.

To make things confusing, there is also NavigatorExperimental (yes, that’s different from Ex-Navigation) and ExNavigator (which was made by James Ide and Ex-Navigation is based on). The good news is that everyone working on these problems got together and decided to merge them all together. I don’t know how long that is going to take but it will probably be released sometime in the next few months under the name React Navigation, and that should unify everyone’s efforts!

There is also this other school of thought where some people like to use the platform-specific native code for navigation which is the approach that the Wix Navigator uses. I have a strong personal view that its preferable to write UI components like this in JS because I actually think you want your app to be the same across iOS and Android (they are both just black rectangles with touch screens!) and JS tends to make your code more composable and customizable.

Use Ex-Navigation and keep an eye out for React Navigation! Use JS instead of native for this UI code!

Given the increasingly fast development and deployment times, handling API setup for dealing with data is becoming a large obstacle to React Native apps. Do you have any thoughts about the use of Backend-As-A-Service solutions like Firebase compared to rolling your own API with Node/Express, Rails, or similar?

I don’t have a strongly held view on this right now. There are so many solutions that fit the use cases of people with different needs. We’re seeing things getting easier and easier in every direction that you look.

If you want to write your own code and you’re using JS, you can use something like Zeit’s new now stuff to deploy essentially instantly. If you want a more general purpose solution, Heroku is also really easy. And then of course there is AWS and Google Cloud, etc.

It’s trivially easy for React Native apps to communicate with essentially any backend that uses HTTP/JSON since fetch and JSON.parse are built-in.

If you don’t want to write any code, it seems like Firebase has become the most popular solution since Parse announced its shutdown. One nice thing about Firebase is that you can use their hosted database stuff with React Native using just JS, which means it works just fine with Exponent. Someone wrote up a guide to how to do this here: https://gist.github.com/sushiisumii/d2fd4ae45498592810390b3e05313e5c

Longer term, it seems like something like GraphQL/Relay should become really popular, but that stuff is too hard to setup and use still to be mainstream just yet. I’m not sure whether it will be GraphQL/Relay maturing and getting revised that wins or something else that is slightly different and easy to think about as a developer that comes and beats it, but directionally, it’s definitely right. We built something like this at Quora and it saved a ton of development time.

I would just use whatever you are most comfortable with – almost anything will work! React Native is really similar to the the web in terms of its client capabilities and so I would just think about a React Native or Exponent app as being mostly like a website.

One of the most common problems that I run into when using Redux is trying to figure out why an action is not being captured by a reducer. For someone just getting starting with Redux, debugging this issue can be especially overwhelming because of how Redux manages data flow. So before you start pouring over configuration code, or the logic contained in your action creators and reducers, please, make sure your action types are defined and spelled correctly.

One of the most common problems that I run into when using Redux is trying to figure out why an action is not being captured by a reducer. For someone just getting starting with Redux, debugging this issue can be especially overwhelming because of how Redux manages data flow. So before you start pouring over configuration code, or the logic contained in your action creators and reducers, please, make sure your action types are defined and spelled correctly.

In any application that I have built, most bugs that I have run into are simply due to typos. However, the solution to this particular problem is harder to spot because no errors are raised when the application is run. Take a look at the snippet below.

// actionTypes.js

export const FETCH_FILE_REQUEST = 'fetch_file_request';
export const FETCH_FILE_SUCCESS = 'fetch_file_success';
export const FETCH_FILE_FAIL = 'fetch_file_fail';


// filesReducer.js

import {
  FETCH_FILE_REQUEST,
  FETCH_FILE_SUCESS,
  FETCH_FILE_FAIL
} from '../actions/actionTypes';

const filesReducer = (state = {}, action) => {
  switch (action.type) {
    case FETCH_FILE_SUCESS:
      return { ...state, file: action.payload };
    default:
      return state;
  }
}

export default filesReducer;

Assuming we dispatched an action with type FETCH_FILE_SUCCESS, the filesReducer should catch the action before the default case is returned. But what if that is not happening? Where do we start the debugging process. There does not appear to be anything wrong with the code in the reducer; the action type was imported and matches the case in the switch statement. There are no errors in the browser. Where is the issue?

You may have noticed that I misspelled SUCCESS in filesReducer.js, but the reason this can be hard to catch is because importing undefined types does not cause an error, so when we import FETCH_FILE_SUCESS, its value is actually undefined, so our reducer always hits the default case.

It would be nice if the existing import/export system could help us catch this. Unfortunately, since action types are just strings, validating their existence is challenging. Luckily, we have another option.

Enter Proxies

Proxies are a feature of ES2015 that allow us to customize operations on a object. They can be used in many different ways, and you can find some useful examples here and here. For our problem, this example from Mozilla looks promising:

let validator = {
  set: function(obj, prop, value) {
    if (prop === 'age') {
      if (!Number.isInteger(value)) {
        throw new TypeError('The age is not an integer');
      }
      if (value > 200) {
        throw new RangeError('The age seems invalid');
      }
    }

    // The default behavior to store the value
    obj[prop] = value;

    // Indicate success
    return true;
  }
};

let person = new Proxy({}, validator);

person.age = 100;
console.log(person.age); // 100
person.age = 'young'; // Throws an exception
person.age = 300; // Throws an exception

So if proxies can be used to validate that properties assigned to an object are of a certain type and value, we should definitely be able to ensure that our action types are never undefined, or else throw an error that will be easy for us to fix. Let’s refactor our actionTypes.js file.

// actionTypes.js

const types = {
  FETCH_FILE_REQUEST: 'fetch_file_request',
  FETCH_FILE_SUCCESS: 'fetch_file_success',
  FETCH_FILE_FAIL: 'fetch_file_fail'
}

const typeValidator = {
  get(obj, prop) {
    if (obj[prop]) {
      return prop;
    } else {
      throw new TypeError(`${prop} is not a valid action type`);
    }
  }
}

module.exports = new Proxy(types, typeValidator);

First, we define a object containing all our action types. Then we define our validator handler typeValidator. The get method inside our handler is called a trap, and provides access to the properties of a object. If the property we are looking for, an action type, in this case, exists in the types object, return that prop, unmodified. Otherwise, throw an error because the prop does not exist.

Finally, export a new proxy, passing the types object as the target and the typeValidator as the handler. However, it is important to note that the ES2015 module system does not work well with proxies, so module.exports and require() must be used for exporting and importing the types.

Barely any code needs to change in the reducer and action creator files, but in order for the action types to be imported successfully, we just need couple lines of code in a new file:

// actionTypesProxy.js

export const {
  FETCH_FILE_REQUEST,
  FETCH_FILE_SUCCESS,
  FETCH_FILE_FAIL,
} = require('./actionTypes');

// in the reducer and action creator files
// change '../actions/actionTypes' to
// '../actions/actionTypesProxy'

By creating a proxy to verify the existence of an action type, we no longer have to worry about correctly naming a property upon import because an error will be thrown in the browser console as soon as the application starts. So, reduce the number headaches you get when developing an application using Redux and start using proxies.

Interested in learning how to build applications using Redux with ReactJS. Check out this online course! Modern React with Redux