What is the architectural pattern MVVM?

MVVM (Model-View-ViewModel) is an architectural pattern that divides an application into three interconnected components:

1. Model: Represents the data and business logic of the application. It is independent of View and ViewModel.
2. View: Represents the user interface (HTML, CSS). The View is passive and contains no logic. It displays data from the ViewModel and sends user actions.
3. ViewModel: Acts as an intermediary between the Model and the View. It contains the presentation logic and handles user actions. The ViewModel provides data to the View in a format suitable for display and updates the Model in response to user actions. The ViewModel does not know about the existence of a specific View.

A key feature of MVVM is Data Binding. The View and ViewModel are linked so that changes in the ViewModel are automatically reflected in the View, and vice versa.

Advantages of MVVM:

• Separation of concerns: Clearly separates UI from business logic.
• Testability: The ViewModel is easily testable independently of the UI.
• Maintainability: Simplifies making changes to the UI or logic.
• Reusability: The ViewModel can be used with different Views.

MVVM is widely used in modern frontend frameworks such as Vue.js and Angular (where the ViewModel often corresponds to the component controller).