Function useMemo

packages/react-server/src/ReactFizzHooks.js:443–471

(nextCreate: () => T, deps: Array<mixed> | void | null)

}

function useMemo<T>(nextCreate: () => T, deps: Array<mixed> | void | null): T {
  currentlyRenderingComponent = resolveCurrentlyRenderingComponent();
  workInProgressHook = createWorkInProgressHook();

  const nextDeps = deps === undefined ? null : deps;

  if (workInProgressHook !== null) {
    const prevState = workInProgressHook.memoizedState;
    if (prevState !== null) {
      if (nextDeps !== null) {
        const prevDeps = prevState[1];
        if (areHookInputsEqual(nextDeps, prevDeps)) {
          return prevState[0];
        }
      }
    }
  }

  if (__DEV__) {
    isInHookUserCodeInDev = true;
  }
  const nextValue = nextCreate();
  if (__DEV__) {
    isInHookUserCodeInDev = false;
  }
  // $FlowFixMe[incompatible-use] found when upgrading Flow
  workInProgressHook.memoizedState = [nextValue, nextDeps];
  return nextValue;
}

function useRef<T>(initialValue: T): {current: T} {
  currentlyRenderingComponent = resolveCurrentlyRenderingComponent();