Answers for "npm install @"

install npm

sudo apt update  ## Update apt Repository
sudo apt install npm ## Install NPM in the apt Repository
sudo npm install -g npm ## Update the NPM to Latest Stable version

npm install

npm install -g sass

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

what is npm install

npm install module-name
npm i module-name
puts module-name package (js library file) 
into node_modules folder
so you can require it in node app