React

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React v0.9 RC

February 16, 2014 by Ben Alpert

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:

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 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:

<div>
  Monkeys:
  {listOfMonkeys} {submitButton}
</div>

In v0.8 and below, it was transformed to the following:

React.DOM.div(null,
  " Monkeys: ",
  listOfMonkeys, submitButton
)

In v0.9, it will be transformed to this JS instead:

React.DOM.div(null,
  "Monkeys:",
  listOfMonkeys, " ", submitButton
)

We believe this new behavior is more helpful and elimates 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 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 <html> 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 <meta> tags
    • sandbox, seamless, and srcDoc for <iframe> tags
    • scope for screen readers
    • span for <colgroup> tags
  • Added support for defining propTypes in mixins
  • Added any, arrayOf, component, oneOfType, renderable, shape to React.PropTypes
  • Added support for statics on component spec for static component methods
  • On all events, .currentTarget is now properly set
  • On keyboard events, .key is now polyfilled in all browsers for special (non-printable) keys
  • On clipboard events, .clipboardData is now polyfilled in IE
  • On drag events, .dataTransfer is now present
  • Added support for onMouseOver and onMouseOut in addition to the existing onMouseEnter and onMouseLeave events
  • Added support for onLoad and onError on <img> elements
  • Added support for onReset on <form> elements
  • The autoFocus attribute is now polyfilled consistently on input, select, and textarea

Bug Fixes #

  • React no longer adds an __owner__ property to each component's props object; passed-in props are now never mutated
  • When nesting top-level components (e.g., calling React.renderComponent within componentDidMount), events now properly bubble to the parent component
  • Fixed a case where nesting top-level components would throw an error when updating
  • Passing an invalid or misspelled propTypes type now throws an error
  • On mouse enter/leave events, .target, .relatedTarget, and .type are now set properly
  • On composition events, .data is now properly normalized in IE9 and IE10
  • CSS property values no longer have px appended for the unitless properties columnCount, flex, flexGrow, flexShrink, lineClamp, order, widows
  • Fixed a memory leak when unmounting children with a componentWillUnmount handler
  • Fixed a memory leak when renderComponentToString would store event handlers
  • Fixed an error that could be thrown when removing form elements during a click handler
  • key values containing . are now supported
  • Shortened data-reactid values for performance
  • Components now always remount when the key property changes
  • Event handlers are attached to document only when necessary, improving performance in some cases
  • Events no longer use .returnValue in modern browsers, eliminating a warning in Chrome
  • scrollLeft and scrollTop are no longer accessed on document.body, eliminating a warning in Chrome
  • General performance fixes, memory optimizations, improvements to warnings and error messages

React with Addons #

  • React.addons.TransitionGroup was renamed to React.addons.CSSTransitionGroup
  • React.addons.TransitionGroup was added as a more general animation wrapper
  • React.addons.cloneWithProps was added for cloning components and modifying their props
  • Bug fix for adding back nodes during an exit transition for CSSTransitionGroup
  • Bug fix for changing transitionLeave in CSSTransitionGroup
  • Performance optimizations for CSSTransitionGroup
  • On checkbox <input> elements, checkedLink is now supported for two-way binding

JSX Compiler and react-tools Package #

  • Whitespace normalization has changed; now space between two tags on the same line will be preserved, while newlines between two tags will be removed
  • The react-tools npm package no longer includes the React core libraries; use the react package instead.
  • displayName is now added in more cases, improving error messages and names in the React Dev Tools
  • Fixed an issue where an invalid token error was thrown after a JSX closing tag
  • JSXTransformer now uses source maps automatically in modern browsers
  • JSXTransformer error messages now include the filename and problematic line contents when a file fails to parse