What problems does javascript frameworks like React/Angular solve?

Question

I am new to React js and I have been trying to understand what real problem does js frameworks like React,Angular solve and why one need to learn them.

Of Course when i see advantages of framework everybody talk about "Shadow/Virtual DOM, Router, Reusable Components etc" , but then I stumbled upon below links which talk something different

https://medium.com/dailyjs/the-deepest-reason-why-modern-javascript-frameworks-exist-933b86ebc445

https://www.codementor.io/binarymuse/react-components-from-a-jquery-programmer-background-du107k2lz

but they were not clear to me

So i am meaning to understand how difficult it was to maintain js/jquery code before these framework came by.

Everybody is just asking to learn these frameworks because they are popular but none of them clearly explains why they are popular and what problem they solve and how they make our life easier when it comes to creating web-app from scratch.

Answer 1

Others have already mentioned the advantages and what these frameworks resolve.

I wanted to add what problems they can create:

1. I have seen many people that use a framework see it as a hammer and every website as a nail. In other words they either don't or can't figure out that in many cases a framework is not needed. I have seen web pages that are nearly 90% static data still download an entire framework just to provide drop menus or something else trivial.
2. Frameworks force you into a lifecycle and development style that, in some ways, make some things easier and other things much, much more complicated. AngularJS had a nasty digest cycle that often led to complications. Redux forces you to write much more code than needed just to handle state that on many pages is not needed. Vue, React, Angular all force you to either use their data creation functions, their way of rendering or their way of handling inter element communication. And none of these are faster than vanillaJS. Even virtual DOM has its issues.
3. The size of a framework is often much more than needed. I have several small libraries that do the majority of the work that a framework does but my code is in the sub 5K range if I load it all.
4. Some people that learn a framework first can not figure out how to write in raw JavaScript. They also tend to learn sloppy ways to write code. No, not everyone, but a large number people that did not start with vanilla JS write code that tends to be much larger and sloppier than needed.
5. It is best to avoid JavaScript except where really needed. Often I can use raw HTML and CSS to do everything I need to do. I find that it is rare that I need to use much JavaScript even in projects that exceed several thousand files. It is faster to allow the browser to process HTML and CSS, which all processes at compiled speeds and only use JavaScript for things you can not do in HTML and CSS.