rerender-memo

Imported from Team-Managed/fheENV (fheenv/frontend/.agents/skills/rerender-memo/SKILL.md). Install upstream with npx skills add Team-Managed/fheENV --skill rerender-memo. Copyright stays with the author.

Extract to Memoized Components

Extract expensive work into memoized components to enable early returns before computation.

Incorrect (computes avatar even when loading):

function Profile({ user, loading }: Props) {
  const avatar = useMemo(() => {
    const id = computeAvatarId(user);
    return <Avatar id={id} />;
  }, [user]);

  if (loading) return <Skeleton />;
  return <div>{avatar}</div>;
}

Correct (skips computation when loading):

const UserAvatar = memo(function UserAvatar({ user }: { user: User }) {
  const id = useMemo(() => computeAvatarId(user), [user]);
  return <Avatar id={id} />;
});

function Profile({ user, loading }: Props) {
  if (loading) return <Skeleton />;
  return (
    <div>
      <UserAvatar user={user} />
    </div>
  );
}

Note: If your project has React Compiler enabled, manual memoization with memo() and useMemo() is not necessary. The compiler automatically optimizes re-renders.