what does yarn install do code example

Example 1: install yarn

npm install -g yarn

Example 2: yarn add install all packages in package,json

yarn install

Example 3: yarn save dev

yarn add <package...> [--dev/-D]

Example 4: install yarn

curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list