Guidline @ Reference Step By Step Deploy Node JS onto Digital Ocean

 https://medium.com/nerd-for-tech/deploy-your-nodejs-application-to-a-digital-ocean-droplet-step-by-step-guide-3f6f928f776

Install latest node JS in Ubuntu --> Digital Ocean

 //STEP 1:install using curl (PPA)

sudo apt update && sudo apt install curl -y

//STEP 2:install latest version (replace 14.x with requird one(i.e 15.x))

curl -sL https://deb.nodesource.com/setup_15.x | sudo -E bash -

sudo apt install nodejs

nodejs -v

v15.3.0

Check array if exist & Undefined - JS