Question

You're migrating a large React class component to hooks with an AI agent, one component at a time. The agent confidently converts `componentDidUpdate(prevProps)` logic into a `useEffect`. Below is a sketch of what it produced — explain what behavior changed and how you'd catch it.

1// BEFORE (class)2componentDidUpdate(prevProps) {3  if (prevProps.userId !== this.props.userId) {4    this.fetchUser(this.props.userId);5  }6}7 8// AFTER (agent's hook)9useEffect(() => {10  fetchUser(userId);11}, [userId, fetchUser]);