Preact 6

Features

• Preliminary React DevTools support thanks to the amazing @robertknight! 🙇

Fixes

• Prevent against reassignment of the same value to TextNodes in Firefox (#368, thanks @zbinlin)
• When swapping the base of a composed child component, update its parent's base reference (#349)
• Prevent accidental duplicate recycling of elements when swapping a component's root element (#373, thanks @jakearchibald)

With 6.3.0, the children prop (on a VNode) is now always an Array, even if there are no children. This allows us to skip an existence check when plucking children within render:

// 6.2.1 & prior:
({ children }) => children && children[0];

// As of 6.3.0:
({ children }) => children[0];

This change is backwards compatible since previously an empty array was already being returned for no children in some cases. Now it's just more consistent! 🌈

Bugfix: Switch to using the render parent to determine if re-rendering starting from within an SVG, since the current element may not exist (eg: for a component).

Improvements

• Support for infinitely nested children!
• Massive performance boost for h() (the hyperscript/jsx processor/reviver).
• Tons of little performance optimizations
• Allow components to not inherit from Component without caring
• Add aliases.js and typings.json to the NPM package.

Public Changes

• Rename Component._disableRendering to Component._disable to save a few bytes
• Removed undocumented support for getInitialState() on classful components.

This has never been part of the API but was left in core in order to support preact-compat's use. It is now being moved into preact-compat. This allows preact to normalize class components that don't inherit from Component.

Bugfixes

• Fix regression in 6.1.0 where state changes in componentDidUpdate() resulted in synchronous re-renders
• Fix issue where rendering an SVG element using the className prop (alias) would incorrectly assign className as an attribute. /cc @pl12133
• Fix serializing class for SVG (test included) (#334)

• Tons of little optimizations!
• Don't skip empty values in extend() (and thus in setState()). Fixes #308.
• Address ownership issue when rendering using reclaimed DOM. Fixes #297.
• Fix issue where re-rendering an intermediary high order component could remove (or fail to add) the associated element.
• When removing old props from the DOM, skip those with empty values.
• Exclusively rely on DOM state when diffing value and checked props. Fixes #326.
• Use strict equality when comparing attribute values against prop values. Fixes #327.
• Upon initial entry into diff, check if the diff should start out in SVG mode. Fixes #331.
• Fix prop cache reset triggering in the wrong case (affected performance)
• Add typings path to package.json. Fixes #318.
• Add support for single level of array children in h() (#313)
• Move both className to class normalization and hashed class stringification out of h() and into the DOM renderer.
  • Tiny possible breakage here: if you were creating VNodes using className and expecting them to have attributes.class instead of attributes.className, that is no longer the case.

• Fix <input list="id"> when datalist element is placed after the input in the DOM (Issue #294, thanks @vutran!)
• Fix HMR issue caused by recycling of a re-used Component base. (Issue #295, thanks @katopz!)

• Make 6.x the official latest release!

npm install --save preact@beta

Features

• Add support for SVG <foreignObject> (#278, thanks @amio!)
• Add preact/aliases import: A copy of preact that includes a createElement() alias (#168/#274, thanks @ngasull!)
• Switch to use event capturing for increased consistency with React (#266/#271, thanks @i-like-robots!)

Breaking Changes

• Discard keyed nodes when diffing children instead of allowing them to be reused unkeyed
• linkState() no longer falls back to components path lookups and no longer auto-invokes functions
  • These features were unused & poorly documented, and added extra weight
• Remove default empty options.vnode hook
  • While this is technically a breaking change, very few people use this API
  • Simply perform an existence check on the previous hook prior to calling it

Bug Fixes

• Fix and tests for regression in 5.7 that could cause nodes to be removed (related to #260/#277)
• Fix initial render failing to reuse certain components when picking up from SSR (#260)
• When swapping between Text, Comment and Element nodes, recycle whole orphaned trees
• Prevent the recycler from collecting non-Element nodes 🐛
• Switch back to the pre-5.7 case-sensitive on prefix for event handler props (#275, thanks @c2h5oh!)