I have read that an enumerable property is something that can be iterated over, so is an enumerable function a function that can also be iterated over, or, a function that performs the iteration?
Below is a reference to a Backbone article that mentions enumerable functions:
https://developers.supportbee.com/singlepageapp/introduction-to-backbone/
And the text reads
Backbone.js gives structure to web applications by providing models with key-value binding and custom events, collections with a rich API of enumerable functions, views with declarative event handling, and connects it all to your existing API over a RESTful JSON interface.