Jwt its json web token normally used for implementing authentication, (logging in) it returns a long string which is returned whenever a user hits the log in route and attempt a login,

Separate your front end from your back end Unless you are using next.js. Don't use variables in your code create constants.js in every file and store your variables there then you can import to your code. Use prettier and lint for cleaner code. The list goes on and on

You are welcome

Just download node from there website and install that's all, it comes with npm to help you install pakages

I don't think it's even cool trying to compare both, the have there strength and weaknesses even there is still a work around in there weakness. So for me I think you should work with what's more comfortable for you, I have tried both and I will tell you that the are both OK but I will prefer node because it has a brighter future PHP is wearing off doesn't mean people are not still using it, Facebook still run on PHP. So my opinion is go with what you are comfortable with

Little hack for you. Check you proxy you might be behind a proxy If not then try npm cache clean --force then run the install again