Rect ![](https://images.velog.io/images/yellowelly/post/b33bc296-1469-486b-8f1a-58a2a8a945a8/%E1%84%89%E1%85%B3%E1%84%8F%E1%85%B3%E1%84%85%E1%85%B5%E
1. React single-Page-Applications(SPAs) Sever only one HTML page, therafter, React takes over and controls the UI. Lean and foc
constructor/ useEffect / Hook