React v0.11 RC

July 13, 2014 by Paul O’Shannessy

It’s that time again… we’re just about ready to ship a new React release! v0.11 includes a wide array of bug fixes and features. We highlighted some of the most important changes below, along with the full changelog.

The release candidate is available for download from the CDN:

React
Dev build with warnings: https://fb.me/react-0.11.0-rc1.js
Minified build for production: https://fb.me/react-0.11.0-rc1.min.js
React with Add-Ons
Dev build with warnings: https://fb.me/react-with-addons-0.11.0-rc1.js
Minified build for production: https://fb.me/react-with-addons-0.11.0-rc1.min.js
In-Browser JSX transformer
https://fb.me/JSXTransformer-0.11.0-rc1.js

We’ve also published version 0.11.0-rc1 of the react and react-tools packages on npm and the react package on bower.

Please try these builds out and file an issue on GitHub if you see anything awry.

`getDefaultProps`

Starting in React 0.11, getDefaultProps() is called only once when React.createClass() is called, instead of each time a component is rendered. This means that getDefaultProps() can no longer vary its return value based on this.props and any objects will be shared across all instances. This change improves performance and will make it possible in the future to do PropTypes checks earlier in the rendering process, allowing us to give better error messages.

Rendering to `null`

Since React’s release, people have been using work arounds to “render nothing”. Usually this means returning an empty <div/> or <span/>. Some people even got clever and started returning <noscript/> to avoid extraneous DOM nodes. We finally provided a “blessed” solution that allows developers to write meaningful code. Returning null is an explicit indication to React that you do not want anything rendered. Behind the scenes we make this work with a <noscript> element, though in the future we hope to not put anything in the document. In the mean time, <noscript> elements do not affect layout in any way, so you can feel safe using null today!

// Before
render: function() {
  if (!this.state.visible) {
    return <span/>;
  }
  // ...
}

// After
render: function() {
  if (!this.state.visible) {
    return null;
  }
  // ...
}

JSX Namespacing

Another feature request we’ve been hearing for a long time is the ability to have namespaces in JSX. Given that JSX is just JavaScript, we didn’t want to use XML namespacing. Instead we opted for a standard JS approach: object property access. Instead of assigning variables to access components stored in an object (such as a component library), you can now use the component directly as <Namespace.Component/>.

// Before
var UI = require('UI');
var UILayout = UI.Layout;
var UIButton = UI.Button;
var UILabel = UI.Label;

render: function() {
  return <UILayout><UIButton /><UILabel>text</UILabel></UILayout>;
}

// After
var UI = require('UI');

render: function() {
  return <UI.Layout><UI.Button /><UI.Label>text</UI.Label></UI.Layout>;
}

Improved keyboard event normalization

Keyboard events now contain a normalized e.key value according to the DOM Level 3 Events spec, allowing you to write simpler key handling code that works in all browsers, such as:

handleKeyDown: function(e) {
  if (e.key === 'Enter') {
    // Handle enter key
  } else if (e.key === ' ') {
    // Handle spacebar
  } else if (e.key === 'ArrowLeft') {
    // Handle left arrow
  }
},

Keyboard and mouse events also now include a normalized e.getModifierState() that works consistently across browsers.

Changelog

React Core

Breaking Changes

getDefaultProps() is now called once per class and shared across all instances

New Features

Rendering to null
Keyboard events include normalized e.key and e.getModifierState() properties
New normalized onBeforeInput event
React.Children.count has been added as a helper for counting the number of children

Bug Fixes

Re-renders are batched in more cases
Events: e.view properly normalized
Added Support for more HTML attributes (coords, crossOrigin, download, hrefLang, mediaGroup, muted, scrolling, shape, srcSet, start, useMap)
Improved SVG support
- Changing className on a mounted SVG component now works correctly
- Added support for elements mask and tspan
- Added support for attributes dx, dy, fillOpacity, fontFamily, fontSize, markerEnd, markerMid, markerStart, opacity, patternContentUnits, patternUnits, preserveAspectRatio, strokeDasharray, strokeOpacity
CSS property names with vendor prefixes (Webkit, ms, Moz, O) are now handled properly
Duplicate keys no longer cause a hard error; now a warning is logged (and only one of the children with the same key is shown)
img event listeners are now unbound properly, preventing the error “Two valid but unequal nodes with the same data-reactid”
Added explicit warning when missing polyfills

React With Addons

PureRenderMixin
Perf: a new set of tools to help with performance analysis
Update: New $apply command to transform values
TransitionGroup bug fixes with null elements, Android

React NPM Module

Now includes the pre-built packages under dist/.
envify is properly listed as a dependency instead of a peer dependency

JSX

Added support for namespaces, eg <Components.Checkbox />
JSXTransformer
- Enable the same harmony features available in the command line with <script type="text/jsx;harmony=true">
- Scripts are downloaded in parallel for more speed. They are still executed in order (as you would expect with normal script tags)
- Fixed a bug preventing sourcemaps from working in Firefox

React Tools Module

Improved readme with usage and API information
Improved ES6 transforms available with --harmony option
Added --source-map-inline option to the jsx executable
New transformWithDetails API which gives access to the raw sourcemap data

getDefaultProps

Rendering to null