Single Page Application (SPA) is the greatest sensation at the moment. We have countless JavaScript frameworks available to ease our work. We cannot deny that JavaScript, as just a scripting language, has become the largest technology evolution since the rise of the Web, and of course, the browser's support is much better than the old times. Now, we can use the JavaScript language on both sides, that is, from the frontend to the backend (Node.js) and also include databases with MongoDB (we will talk about them briefly in the next chapters). Now, we focus on understanding the MVC/MVVM pattern on SPA. We will cover the following topics: