https://challenage-barryyu.web.app/ 會使用到 reducer ,,switch()case : default return , state.findIndex (),, action.type , reduce , splice , router-DOM , dispatch( ( ) ) , github : 每一個階段都是辛苦的研究和筆記 https://github.com/DoungBarry/amazon_challenage-BarryYu