What Is MVC?

What Is MVC?

A number of modern JavaScript frameworks provide developers an easy path to organizing their code using variations of a pattern known as MVC (Model-View-Controller). MVC separates the concerns in an application into three parts:

• Models represent the domain-specific knowledge and data in an application. Think of this as being a type of data you can model — like a User, Photo, or Todo note. Models can notify observers when their state changes.
• Views typically constitute the user interface in an application (e.g., markup and templates), but don’t have to be. They observe Models, but don’t directly communicate with them.
• Controllers handle input (e.g., clicks, user actions) and update Models.

Thus, in an MVC application, user input is acted upon by Controllers which update Models. Views observe Models and update the user interface when changes occur.

JavaScript MVC frameworks don’t always strictly follow the above pattern. Some solutions (including Backbone.js) merge the responsibility of the Controller into the View, while other approaches add additional components into the mix.

For this reason we refer to such frameworks as following the MV* pattern; that is, you’re likely to have a Model and a View, but a distinct Controller might not be present and other components may come into play.