Question

I am trying to understand the difference between Model and ViewModel in KO. I understand the conceptual difference, but to me it seems that all Models in KO will become or are candidates to become ViewModels. Ill explain:

Say you have a table with a row of seats, so in your main ViewModel you will initialise and load a collection of objects from a Seat Model into an observable array.

Now you want to hide display seats based on a certain property of seats…this is the point where your model becomes another viewmodel…

So is it right to say that in KO all we have is ViewModels?

Answer 1

Yes. Essentially, anything with a ko.observable is creating a ViewModel. You could create a simple javascript model expressible as nothing but JSON, and wrap it, but the “model” in Knockout’s MVVM pattern generally exists only on the server. You get the model data from the server, and you send model data back to the server (remember, you don’t send the observables, just their data)

Knockout doesn’t really care about where the model comes from, because its primary role is to deal with the databinding between the declarative view (HTML) and the ViewModel (with its View-aware observables).

The MVVM pattern is completed by technology outside of Knockout, since it’s a client-side only framework. You could say that it is just the VVM part of the pattern, but that is confusing.