If they are not pure, you are literally making an error (as the framework states they are supposed to be pure).
input-process-output is how pure functional languages (such as Haskell) deal with imperative coding. You push the imperative part to the top of the call stack and try to keep the rest of the computation pure.
JavaScript inherited quite a bit from Smalltalk, so you will find similarities like these in JS in general.
Flux supplements the standard React bubbling of events up the chain of components with a simpler, singular flow, making it even more functional.
input-process-output is how pure functional languages (such as Haskell) deal with imperative coding. You push the imperative part to the top of the call stack and try to keep the rest of the computation pure.
JavaScript inherited quite a bit from Smalltalk, so you will find similarities like these in JS in general.
Flux supplements the standard React bubbling of events up the chain of components with a simpler, singular flow, making it even more functional.