[merrywhether]

fb.js is Facebook’s standard JS base, with things like polyfills/ponyfills to ensure certain features in a browser environment. It’s imported by React, Relay, etc.

So this might be what you’re seeing, but normally it’s included in a precompiled JS application bundle.

[jacobwg]

I believe you're thinking of FBJS (https://github.com/facebook/fbjs), which is a library as you describe, whereas the comment above is referring to loading the Facebook SDK from Facebook's servers. Among other things, Netflix offers Facebook login, which would need the SDK loaded.