I add web3 package to my react project and start.
yarn add web3
yarn start
But it causes following errors:
...
BREAKING CHANGE: webpack < 5 used to include polyfills for node.js core modules by default.
...
I fixed these issues for 4 days. Then I found the reason of this problem.
I changed to lower version of mainly 2 of packages - react-router-dom
and react-scripts
.
ex:
react-scripts - 5.0.0 : error causes
react-scripts - 4.0.3 : success