Along with React, GraphQL and a bunch of other technologies with various degrees of popularity https://opensource.fb.com
Along with various startups building around the projects incubated at Facebook - Asana, Interana, Phacility, Qubole, etc.
Where B is the sum of the set consisting of:
-Breaking democracy in the US and the UK by being _the_ platform for disinformation.
-Disinformation assisting genocide in Myanmar.
-Use correlating strongly with poor mental health
-Manipulating behaviour to encourage poor attention spans for the sake of ad-clicking
-Constantly violating basic standards of privacy
-(I could go on..)
Oh wait, excuse my arithmetic. I forgot to add another JS framework like Relay to the LHS of the equation, that makes it a net positive from Facebook! :D