Flux is an idea, there's multiple implementations because they optimize for different concerns. For example, I like Fluxible because it lets you do server side

Flux is an idea, there's multiple implementations because they optimize for different concerns. For example, I like Fluxible because it lets you do server side rendering, and it avoids singletons, so it's exceptionally easy to test. However, if I'm working on an app that doesn't have any public facing components, I'd probably consider a different implementation that is less verbose.