Hello, @zchan,
I have just checked our Quickstarts and neither our Node.js nor our Javascript Quickstart reference the request module. We also don’t have any examples using https.
As I mentioned, I recommend that you use whatever modules that you want to use, but reference the Authentication API Explorer in order to build a call according to specifications. You can use absolutely any module or package of your preference.
Finally, I would like to emphasize the fact that the Client Credentials grant is supposed to be used in a Machine to Machine scenario, and not when the application is authenticating on behalf of a user. It should only be used when a machine wants to authenticate on behalf of itself.