Error : Failed to load bundle localhost:8081

I have same issue. I tried to install

npm add @babel/runtime

then

npm install

It works for me, i hope it helps you.

Sometimes different programs use same ports like 80,8080 or 8081, when I face this problem I set the default port to 8088. And It works perfect.

Try

react-native run-ios --port=8088

If changing port isn't work, try this. This will install the @babel/runtime package to your project.

npm add @babel/runtime

npm install

After this re-compile your project.

I hope it works.

Soluton that works:

rm -rf ios/build/; kill $(lsof -t -i:8081)