Javascript Package - Dev Dependency

A dev dependency is a build and test dependency.

They

• are not needed in the dependency graph (bundler, test harnesses or transpilers)
• will not be downloaded when an other package uses your package as a dependency.

This command will modify the devependency properties of package.json

cd DirectoryOfPackage.Json
# then
yarn add [package] --dev
# or
npm install packageName --save-dev