Immutable.js v4.0.0-rc.1 发布了，这是一个预览版，因此这里的更新日志不会包含所有的更新内容，查看提交记录以了解完整更新内容。更新内容如下：
Iterableclass has been renamed to
isIterable()has been renamed to
isCollection(). Aliases with the existing names exist to make transitioning code easier.
The "predicate" functions,
isAssociativehave been moved from
Iterable.to the top level exports.
Record is no longer an Immutable Collection type.
The sequence API (such as
forEach) no longer exist on Records.
clear()no longer exist on Records.
toJSON()method is now a shallow conversion (previously it was an alias for
toJS(), which remains a deep conversion).
Some minor implementation details have changed, which may require updates to libraries which deeply integrate with Immutable.js's private APIs.
The Cursor API is officially deprecated. Use immutable-cursor instead.
A new predicate function
isValueObject()helps to detect objects which implement
hashCode(), and type definitions now define the interface
ValueObjectwhich you can implement in your own code to create objects which behave as values and can be keys in Maps or entries in Sets.
The Flowtype and TypeScript type definitions have been completely rewritten with much higher quality and accuracy, taking advantage of the latest features from both amazing tools.
fromJS()with a "reviver" function now provides access to the key path to each translated value. (#1118)
Numerous bug fixes have gone into this release