install nodejs on Debian 9

gistfile1.txt

With Sudo
$ curl -sL https://deb.nodesource.com/setup_10.x | sudo -E bash -
Without Sudo
$ cd Downloads
$ curl -sL https://deb.nodesource.com/setup_10.x > setup_10.x 
$ chmod +x setup_10.x
# ./setup_10.x
Install NodeJS
So, now that you have the repository set up, you can install NodeJS normally through `apt`.
# apt install nodejs
Test NodeJS
Make sure that Node is installed and working properly. You can check that it's there with the `-v` flag.
$ node -v
Install With NPM
Before you get started with NPM, install some development packages so NPM won't have a problem when it encounters a source package.
# apt install build-essential libssl-dev
Now, you can install anything that's available in the NPM repositories. NPM is a NodeJS package manager, but it also handles loads of other JavaScript packages. Think of it like the JavaScript version of `pip` or Ruby gems. Try installing the Express. It's easily the most widely used NodeJS framwork, and it's a good place to start with Node.
$ npm install express
Like any package manager, NPM will pull in Express along with all of its dependencies.

source https://linuxconfig.org/how-to-install-nodejs-on-debian-9-stretch-linux