I'm sure that you might know what VanillaJs is. I agree that we have to remember the importance of pure javascript and how it works. but, when we kick off a new web project, we don't have enough time to implement all the things we need. Also, if your customer request some modifications later, you have to manage them. Because of these reasons, you have to develop fast as well as considering maintenance of your project. To make this problem simple, MVC / MVVM Javascript frameworks such as Angular, React, Ember, Backbone, etc appear in the industry. They have different features but all of them help us to develop web applications better and faster!