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:
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.
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!
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/>`.
Keyboard events now contain a normalized `e.key` value according to the [DOM Level 3 Events spec](http://www.w3.org/TR/DOM-Level-3-Events/#keys-special), allowing you to write simpler key handling code that works in all browsers, such as:
```js
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.
* 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`"
