Where in the source is useState defined?

useState is defined in [packages/react/src/ReactHooks.js:L66-L72].

The function is exported as:

export function useState<S>(
  initialState: (() => S) | S,
): [S, Dispatch<BasicStateAction<S>>] {
  const dispatcher = resolveDispatcher();
  return dispatcher.useState(initialState);
}

It takes an initial state (either a value or a function that returns a value) and delegates to a dispatcher's useState implementation, returning a tuple with the state value and a dispatch function.

FOLLOW_UPS:

• What does resolveDispatcher return?
• How does useState handle functional initial state?
• Where is the Dispatch type defined?