Our application's data models will always have associations between them, which must be represented in our client-side applications, so that they can be manipulated easily and consistently. Ext JS offers the ability to model one-to-one, one-to-many, and many-to-many relationships between Model types.
One-to-many relationships exist when a single entity owns multiple entities of a different type. For example, an author has many books or a recipe has many ingredients. In our example project, we will model the association between users and sales—a user can have many sales and each sale only has one user.