Why are JS frameworks needed?

Question

JavaScript

Hi
I'm studying the web, so far at the level of site layout and I often wonder, so why do we need these frameworks?
I already googled it, but I did not find a satisfactory answer for myself. From the search, I found out that this is a set of ready-made tools, but the same can be said about plugins or jquery, then the plugin turns out to be a small framework? So what? I do the layout using cool plugins and jquery, and if you switch to a framework, then it turns out that all this will not be necessary, because all this can be implemented on a framework. Did I understand correctly?
Please help me figure it out..

Answer 1

Library - code for solving some task, tasks What is a code library?
Plugin - extension of the library if I lack it.
Framework - application framework that affects my project globally, i.e. he not only gives me the solution to a small problem, but also tells me what to write and how to write. Usually there is already a lot written under the hood, due to this, development is accelerated.

Answer 2

JS applications can be very large and developed by dozens of people. So, a framework is, in fact, a generally accepted contract about where everything is and how it works. All developers know about this contract and adhere to it. The framework defines the structure of the application at the file system level and provides tools for compiling and debugging it. Parallax whistles are not usually part of the framework, but the framework itself provides the infrastructure for creating and publishing them. So choosing a popular framework, you will most likely find both parallax and menus, and whatever else you need as a component / module for this framework.
It makes sense to think about the framework if your application supports some kind of business logic. For example, it displays and validates the input form, provides a multi-step flow (xs how to say it in Russian: multi-step flow). In general, it does something in order to collect, validate, process and send user data to the server. (this is not the only, but a common reason to use a framework)
The good old library is also suitable for decorating design elements.