This release focuses on fixing some small bugs that have been uncovered over the past two weeks. I would like to thank everybody involved, specifically members of the community who fixed half of the issues found. Thanks to Ben Alpert, Andrey Popp, and Laurence Rowe for their contributions!
This release is the result of several months of hard work from members of the team and the community. While there are no groundbreaking changes in core, we've worked hard to improve performance and memory usage. We've also worked hard to make sure we are being consistent in our usage of DOM properties.
The biggest change you'll notice as a developer is that we no longer support class in JSX as a way to provide CSS classes. Since this prop was being converted to className at the transform step, it caused some confusion when trying to access it in composite components. As a result we decided to make our DOM properties mirror their counterparts in the JS DOM API. There are a few exceptions where we deviate slightly in an attempt to be consistent internally.
The other major change in v0.5 is that we've added an additional build - react-with-addons - which adds support for some extras that we've been working on including animations and two-way binding. Read more about these addons in the docs.
We added 22 new people to the list of authors since we launched React v0.4.1 nearly 3 months ago. With a total of 48 names in our AUTHORS file, that means we've nearly doubled the number of contributors in that time period. We've seen the number of people contributing to discussion on IRC, mailing lists, Stack Overflow, and GitHub continue rising. We've also had people tell us about talks they've given in their local community about React.
It's been awesome to see the things that people are building with React, and we can't wait to see what you come up with next!
Memory usage improvements - reduced allocations in core which will help with GC pauses
Performance improvements - in addition to speeding things up, we made some tweaks to stay out of slow path code in V8 and Nitro.
Standardized prop -> DOM attribute process. This previously resulting in additional type checking and overhead as well as confusing cases for users. Now we will always convert your value to a string before inserting it into the DOM.
Support for additional DOM properties (charSet, content, form, httpEquiv, rowSpan, autoCapitalize).
Support for additional SVG properties (rx, ry).
Support for using getInitialState and getDefaultProps in mixins.
Support mounting into iframes.
Bug fixes for controlled form components.
Bug fixes for SVG element creation.
Added React.version.
Added React.isValidClass - Used to determine if a value is a valid component constructor.
Removed React.autoBind - This was deprecated in v0.4 and now properly removed.
Renamed React.unmountAndReleaseReactRootNode to React.unmountComponentAtNode.
Began laying down work for refined performance analysis.
Better support for server-side rendering - react-page has helped improve the stability for server-side rendering.
Made it possible to use React in environments enforcing a strict Content Security Policy. This also makes it possible to use React to build Chrome extensions.
Introduced a separate build with several "addons" which we think can help improve the React experience. We plan to deprecate this in the long-term, instead shipping each as standalone pieces. Read more in the docs.
No longer transform class to className as part of the transform! This is a breaking change - if you were using class, you must change this to className or your components will be visually broken.
Added warnings to the in-browser transformer to make it clear it is not intended for production use.
Improved compatibility for Windows
Improved support for maintaining line numbers when transforming.
We organized a React hackathon last week-end in the Facebook Seattle office. 50 people, grouped into 15 teams, came to hack for a day on React. It was a lot of fun and we'll probably organize more in the future.
Alex Swan implemented Qu.izti.me, a multi-player quiz game. It is real-time via Web Socket and mobile friendly.
The game itself is pretty simple. People join the "room" by going to http://qu.izti.me on their device. Large displays will show a leaderboard along with the game, and small displays (such as phones) will act as personal gamepads. Users will see questions and a choice of answers. The faster you answer, the more points you earn.
In my opinion, Socket.io and React go together like chocolate and peanut butter. The page was always an accurate representation of the game object.
Alexander Solovyov has been working on React bindings for ClojureScript. This is really exciting as it is using "native" ClojureScript data structures.
A wrapper around JSHint to allow linting of files containing JSX syntax. Accepts glob patterns. Respects your local .jshintrc file and .gitignore to filter your glob patterns.
Ross Allen working at Mesosphere combined Turbolinks, a library used by Ruby on Rails to speed up page transition, and React.
"Re-request this page" is just a link to the current page. When you click it, Turbolinks intercepts the GET request and fetchs the full page via XHR.
The panel is rendered with a random panel- class on each request, and the progress bar gets a random widthX class.
With Turbolinks alone, the entire
would be replaced, and transitions would not happen. In this little demo though, React adds and removes classes and text, and the attribute changes are animated with CSS transitions. The DOM is otherwise left intact.
You see that React components are defined using a regular JS object. Some properties and methods of the object such as render() have special meanings, the rest is upforgrabs.
A lot has happened in the month since our last update. Here are some of the more interesting things we've found. But first, we have a couple updates before we share links.
First, we are organizing a React Hackathon in Facebook's Seattle office on Saturday September 28. If you want to hack on React, meet some of the team or win some prizes, feel free to join us!
We've also reached a point where there are too many questions for us to handle directly. We're encouraging people to ask questions on StackOverflow using the tag [reactjs]. Many members of the team and community have subscribed to the tag, so feel free to ask questions there. We think these will be more discoverable than Google Groups archives or IRC logs.
Pete Hunt and Jordan Walke were interviewed on Javascript Jabber for an hour. They go over many aspects of React such as 60 FPS, Data binding, Performance, Diffing Algorithm, DOM Manipulation, Node.js support, server-side rendering, JSX, requestAnimationFrame and the community. This is a gold mine of information about React.
PETE: So React was designed all around that. Conceptually, how you build a React app is that every time your data changes, it's like hitting the refresh button in a server-rendered app. What we do is we conceptually throw out all of the markup and event handlers that you've registered and we reset the whole page and then we redraw the entire page. If you're writing a server-rendered app, handling updates is really easy because you hit the refresh button and you're pretty much guaranteed to get what you expect.
MERRICK: That's true. You don't get into these odd states.
PETE: Exactly, exactly. In order to implement that, we communicate it as a fake DOM. What we'll do is rather than throw out the actual browser html and event handlers, we have an internal representation of what the page looks like and then we generate a brand new representation of what we want the page to look like. Then we perform this really, really fast diffing algorithm between those two page representations, DOM representations. Then React will compute the minimum set of DOM mutations it needs to make to bring the page up to date.
Then to finally get to answer your question, that set of DOM mutations then goes into a queue and we can plug in arbitrary flushing strategies for that. For example, when we originally launched React in open source, every setState would immediately trigger a flush to the DOM. That wasn't part of the contract of setState, but that was just our strategy and it worked pretty well. Then this totally awesome open source contributor Ben Alpert at Khan Academy built a new batching strategy which would basically queue up every single DOM update and state change that happened within an event tick and would execute them in bulk at the end of the event tick.
Stoyan Stefanov gave a talk at BrazilJS about React and wrote an article with the content of the presentation. He goes through the difficulties of writing active apps using the DOM API and shows how React handles it.
So how does exactly React deal with it internally? Two crazy ideas - virtual DOM and synthetic events.
You define you components in React. It builds a virtual DOM in JavaScript land which is way more efficient. Then it updates the DOM. (And "virtual DOM" is a very big name for what is simply a JavaScript object with nested key-value pairs)
Data changes. React computes a diff (in JavaScript land, which is, of course, much more efficient) and updates the single table cell that needs to change. React replicates the state of the virtual DOM into the actual DOM only when and where it's necessary. And does it all at once, in most cases in a single tick of the requestAnimationFrame().
What about event handlers? They are synthetic. React uses event delegation to listen way at the top of the React tree. So removing a node in the virtual DOM has no effect on the event handling.
The events are automatically cross-browser (they are React events). They are also much closer to W3C than any browser. That means that for example e.target works, no need to look for the event object or checking whether it's e.target or e.srcElement (IE). Bubbling and capturing phases also work cross browser. React also takes the liberty of making some small fixes, e.g. the event <input onChange> fires when you type, not when blur away from the input. And of course, event delegation is used as the most efficient way to handle events. You know that "thou shall use event delegation" is also commonly given advice for making web apps snappy.
The good thing about the virtual DOM is that it's all in JavaScript land. You build all your UI in JavaScript. Which means it can be rendered on the server side, so you initial view is fast (and any SEO concerns are addressed). Also, if there are especially heavy operations they can be threaded into WebWorkers, which otherwise have no DOM access.
Ben Alpert converted marked, a Markdown Javascript implementation, in React: marked-react. Even without using JSX, the HTML generation is now a lot cleaner. It is also safer as forgetting a call to escape will not introduce an XSS vulnerability.
Vjeux re-implemented the display part of the IRC logger in React. Just 130 lines are needed for a performant infinite scroll with timestamps and color-coded author names.
Ben Newman made a 13-lines wrapper to use React and Meteor together. Meteor handles the real-time data synchronization between client and server. React provides the declarative way to write the interface and only updates the parts of the UI that changed.
This repository defines a Meteor package that automatically integrates the React rendering framework on both the client and the server, to complement or replace the default Handlebars templating system.
The React core is officially agnostic about how you fetch and update your data, so it is far from obvious which approach is the best. This package provides one answer to that question (use Meteor!), and I hope you will find it a compelling combination.
Dependencies will be registered for any data accesses performed by getMeteorState so that the component can be automatically re-rendered whenever the data changes.
Jordan Walke implemented a complete React project creator called react-page. It supports both server-side and client-side rendering, source transform and packaging JSX files using CommonJS modules, and instant reload.
Easy Application Development with React JavaScript
Why Server Rendering?
Faster initial page speed:
Markup displayed before downloading large JavaScript.
Markup can be generated more quickly on a fast server than low power client devices.
Faster Development and Prototyping:
Instantly refresh your app without waiting for any watch scripts or bundlers.
Easy deployment of static content pages/blogs: just archive using recursive wget.
SEO benefits of indexability and perf.
How Does Server Rendering Work?
react-page computes page markup on the server, sends it to the client so the user can see it quickly.
The corresponding JavaScript is then packaged and sent.
The browser runs that JavaScript, so that all of the event handlers, interactions and update code will run seamlessly on top of the server generated markup.
From the developer's (and the user's) perspective, it's just as if the rendering occurred on the client, only faster.
React
