Caplet is the M in “MVC”. It works independently from any other library, and can easily be used with your existing framework/view layer such as AngularJS, ReactJS, RactiveJS, or PaperclipJS (shameless plug).
Caplet doesn’t make any assumptions about your code. It just gives organization to your model relationships in a sane way. It also gives you a relatively higher level of encapsulation for your data, while also encouraging you, but not forcefuly, to follow design patterns that scale quite well.
Caplet has been an evolution of many libraries in the past, which have been used in a few pretty large applications (30k-ish loc). The first version came about sometime around 2013 as mojo-models, and has since been further generalized for all intensive purposes.
The newer, hip version of Caplet has been designed for React, and pairs wells with the Hierarchial nature of React-based applications.
Caplet can be a great companion to Flux. It also serves as a Flux alternative if you enjoy the good ‘ol (and well proven when done right) MVC approach (Caplet (M) + React (VC)).