cant' resolve object-assign

2-5를 따라 구현하다가 npx webpack을 실행하면 다음과 같은 에러가 발생합니다.

ERROR in ./node_modules/react-dom/cjs/react-dom.development.js

Module not found: Error: Can't resolve 'object-assign' in 'S:\study\react-webgame\lecture\node_modules\react-dom\cjs'

 @ ./node_modules/react-dom/cjs/react-dom.development.js 17:14-38

 @ ./node_modules/react-dom/index.js

 @ ./client.jsx

 @ multi ./client



ERROR in ./node_modules/react/cjs/react.development.js

Module not found: Error: Can't resolve 'object-assign' in 'S:\study\react-webgame\lecture\node_modules\react\cjs'

 @ ./node_modules/react/cjs/react.development.js 16:14-38

 @ ./node_modules/react/index.js

 @ ./client.jsx

 @ multi ./client



ERROR in ./node_modules/react-dom/cjs/react-dom.development.js

Module not found: Error: Can't resolve 'scheduler/tracing' in 'S:\study\react-webgame\lecture\node_modules\react-dom\cjs'

 @ ./node_modules/react-dom/cjs/react-dom.development.js 19:14-42

 @ ./node_modules/react-dom/index.js

 @ ./client.jsx

 @ multi ./client

그래서 object-assign을 설치해봐도 에러는 같습니다.