--- title: React v0.9 RC author: spicyj --- We're almost ready to release React v0.9! We're posting a release candidate so that you can test your apps on it; we'd much prefer to find show-stopping bugs now rather than after we release. The release candidate is available for download from the CDN: * **React** Dev build with warnings: Minified build for production: * **React with Add-Ons** Dev build with warnings: Minified build for production: * **In-Browser JSX transformer** We've also published version `0.9.0-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](https://github.com/facebook/react/issues/new) if you see anything awry. ## Upgrade Notes In addition to the changes to React core listed below, we've made a small change to the way JSX interprets whitespace to make things more consistent. With this release, space between two components on the same line will be preserved, while a newline separating a text node from a tag will be eliminated in the output. Consider the code: ```html
Monkeys: {listOfMonkeys} {submitButton}
``` In v0.8 and below, it was transformed to the following: ```javascript React.DOM.div(null, " Monkeys: ", listOfMonkeys, submitButton ) ``` In v0.9, it will be transformed to this JS instead: ```javascript{2,3} React.DOM.div(null, "Monkeys:", listOfMonkeys, " ", submitButton ) ``` We believe this new behavior is more helpful and eliminates cases where unwanted whitespace was previously added. In cases where you want to preserve the space adjacent to a newline, you can write a JS string like `{"Monkeys: "}` in your JSX source. We've included a script to do an automated codemod of your JSX source tree that preserves the old whitespace behavior by adding and removing spaces appropriately. You can [install jsx\_whitespace\_transformer from npm](https://github.com/facebook/react/blob/master/npm-jsx_whitespace_transformer/README.md) and run it over your source tree to modify files in place. The transformed JSX files will preserve your code's existing whitespace behavior. ## Changelog ### React Core #### Breaking Changes - The lifecycle methods `componentDidMount` and `componentDidUpdate` no longer receive the root node as a parameter; use `this.getDOMNode()` instead - Whenever a prop is equal to `undefined`, the default value returned by `getDefaultProps` will now be used instead - `React.unmountAndReleaseReactRootNode` was previously deprecated and has now been removed - `React.renderComponentToString` is now synchronous and returns the generated HTML string - Full-page rendering (that is, rendering the `` tag using React) is now supported only when starting with server-rendered markup - On mouse wheel events, `deltaY` is no longer negated - When prop types validation fails, a warning is logged instead of an error thrown (with the production build of React, the type checks are now skipped for performance) - On `input`, `select`, and `textarea` elements, `.getValue()` is no longer supported; use `.getDOMNode().value` instead - `this.context` on components is now reserved for internal use by React #### New Features - React now never rethrows errors, so stack traces are more accurate and Chrome's purple break-on-error stop sign now works properly - Added a new tool for profiling React components and identifying places where defining `shouldComponentUpdate` can give performance improvements - Added support for SVG tags `defs`, `linearGradient`, `polygon`, `radialGradient`, `stop` - Added support for more attributes: - `noValidate` and `formNoValidate` for forms - `property` for Open Graph `` tags - `sandbox`, `seamless`, and `srcDoc` for `