P.S. I am not looking for SPAs and Server Side Rendering etc. I am also not worried about SEO. It's just an admin panel where logged in people can manage the app and perform certain actions.
What's the simplest JS library that I can use so that my UI code is minimal, simple and doesn't become spaghetti!
Thanks!
My first advice would go with plain vanilla js. After that perhaps try to have some fun and use something new like http://monkberry.js.org/
You could do without a framework. But if you want to have stuff out of the box and work with components that are predefined, you could have a look at ExtJS. For some type of projects, is free. Other than that, just about anything works, because the task is simple.
For Admin Panel you basicly need only datatables and form validation. For the first there is 5kb plain JavaScript library - https://bunnyjs.com/examples/datatable/
Second example about Validation I am going to finish on weekend.
There are actually already many simple packages in BunnyJS, I am just slowly writting docs when have free time, so if you will need any help or anything else, feel free to ask me directly.
Also jQuery with it plugins could be a good option and there are many lightweight plain JS components available on GitHub today.
You could look into vue.js, seems appropriate in your situation.
I think you might be bombing you UI with JS by asking such a question. If you want to have minimal UI code, try to get away from JS as much as possible. Try to do stuff with modern HTML and CSS as much as possible.
This being said, there are many good libraries out there which all try to be good at whatever someone created them for. So it really depends on what actions an admin should be able to perform and how you want to present data. For example if you have a lot of widgets which display editible data, you might want to go with some Flux library, like React. If you have a lot of data you just want to display in a very nice way, give d3 a try. If you have a lot of static content and forms, you don't really have to bother with JS (except you want to load content via AJAX of course).
Maybe you could elaborate a bit on what you plan to do?
Rodrigo
Without pressure, there isn't action
Check out React Admin, it's a whole suite that handles that problem. You just need to configure it, but I warn you, it's not easy you need to learn how to work with that library.