install npm

                                    curl -sL https://deb.nodesource.com/setup_6.x | sudo bash -
curl -sL https://deb.nodesource.com/setup_10.x | sudo -E bash -
sudo apt-get install -y nodejs
sudo apt-get install -y npm

                                    npm install (with no args, in package dir)
npm install [<@scope>/]<name>
npm install [<@scope>/]<name>@<tag>
npm install [<@scope>/]<name>@<version>
npm install [<@scope>/]<name>@<version range>
npm install <git-host>:<git-user>/<repo-name>
npm install <git repo url>
npm install <tarball file>
npm install <tarball url>
npm install <folder>

aliases: npm i, npm add
common options: [-P|--save-prod|-D|--save-dev|-O|--save-optional] [-E|--save-exact] [-B|--save-bundle] [--no-save] [--dry-run]

                                    npm install package-name

To save as a dependency:
npm install package-name --save

                                    $ npm install download

                                    $ npm install
$ git add index.js package.json package-lock.json
$ git commit -m "initialize npm package"
$ git push