How to install npm on the Heroku server?

Question

Greeting to all,

I recently sent an Laravel project with Vuejs to the Heroku server, and I realized that it did not recognize my App.js file where the methods created by Vuejs are, this file is in the public folder, so there was no reason not to work, was actually supposed to work.

Then I realized that I had not installed on the Heroku server the npm and the nodejs, to install these guys in Heroku I know I can use the command heroku run "comando desejado", but the problem is this:

The Heroku server uses Windows or Linux?

If it is linux what would be the most correct way to install these guys?

I’m asking here because I didn’t find in the Heroku documentation.