Built-in React APIs

• createContext lets you define and provide context to the child components. Used withuseContext.
• lazy lets you defer loading a component’s code until it’s rendered for the first time.
• memo lets your component skip re-renders with same props. Used withuseMemo anduseCallback.
• startTransition lets you mark a state update as non-urgent. Similar touseTransition.
• act lets you wrap renders and interactions in tests to ensure updates have processed before making assertions.

Resource APIs

Resources can be accessed by a component without having them as part of their state. For example, a component can read a message from a Promise or read styling information from a context.

To read a value from a resource, use this API:

• use lets you read the value of a resource like aPromise orcontext.

functionMessageComponent({messagePromise}){
constmessage =use(messagePromise);
consttheme =use(ThemeContext);
// ...
}