I've been working with NetSuite Suite Bundler since 2015. At the time authentication to NetSuite's API or NetSuite's RESTlet was accomplished by sending a username and password with each call to NetSuite.

NetSuite (I think in 2017) changed this to also allow Access Token based authentication, instead of a raw username/password. As of January 2019, this is now required; the old username/password mechanism has official been deprecated.

Let's explore how to make API calls with the Access Token based authentication.