babel-loader@8.x is the Webpack integration used for Babel 7.x. Babel 7.x has moved all packages from a babel- prefix to the @babel npm scope.
The error is correct, you have incorrectly installed babel-core instead of @babel/core.
If you wish to install Babel 6.x, you can do
npm install --save-dev babel-loader@7 babel-core
but if you're starting a new project, Babel 7 makes much more sense, so you would ideally do
npm install --save-dev babel-loader @babel/core
Answer from loganfsmyth on Stack Overflow
» npm install babel-loader
babel-loader@8.x is the Webpack integration used for Babel 7.x. Babel 7.x has moved all packages from a babel- prefix to the @babel npm scope.
The error is correct, you have incorrectly installed babel-core instead of @babel/core.
If you wish to install Babel 6.x, you can do
npm install --save-dev babel-loader@7 babel-core
but if you're starting a new project, Babel 7 makes much more sense, so you would ideally do
npm install --save-dev babel-loader @babel/core
I had the same error just 5 minutes ago, I fixed that with reinstalling babel-loader.
npm r babel-loader
npm i babel-loader@7
» npm install workerize-loader
» npm install polymer-webpack-loader