To uninstall a package you have previously installed locally (using npm install <package-name> in the node_modules folder, run
npm uninstall <package-name>
from the project root folder (the folder that contains the node_modules folder).
This operation will also remove the reference in the package.json file.
If the package was a development dependency, listed in the devDependencies of the package.json file, you must use the -D / --save-dev flag to remove it from the file:
npm uninstall -D <package-name>
If the package is installed globally, you need to add the -g / --global flag:
npm uninstall -g <package-name>
for example:
npm uninstall -g webpack
and you can run this command from anywhere you want on your system because the folder where you currently are does not matter.