I am .Net developer and used asp.net web forms so far. I am way behind in new technologies. I need to choose a new path. There are so many new things ( actually not new but new to me 
). JavaScript is must to learn. But after that should I pick ReactJs or Next.js? And there is Angular.Js too?
I think Node.Js is must as well. because you need that for server side Javascript.
I really appreciate guidance from experts.
Several presenters at Next Conf this week quoted this React core team guy (never heard of him before this week), but this is just an opinion and should be treated with all the skepticism that entails.
I happen to agree though. I spent years using vanilla React and cobbling together the various pieces we needed and maintaining a custom Webpack config and I really don’t recommend it. This was an existing Python/jQuery project and we were able to add React into it and gradually rewrite it, which is one of the really cool things about React. It’s just a view library, so it can be inserted in places where frameworks (like Angular or Next) can’t go. But if I were starting a new project, I’d choose Next or Remix. It’s just so much simpler (File-based routing alone is an incredible productivity boost). If you do go with the React ecosystem, you’ll probably want to learn at least the JavaScript basics; before learning React basics; before learning Next.js. I’d also recommend TypeScript, which is (reductively) JS with a type system and extra features. If you’ve used C# you’ll probably find TS very familiar.
So what about Angular? I would probably stick with the React ecosystem. I have nothing against Angular. I used it for years. In fact I worked on Google’s Angular Material team in 2014 when we released ngMaterial 1.0. Angular was much simpler back then, but I did use it to build something a couple of years ago. Maybe things have changed since then, but from my memory I find Next.js a far simpler and easier to development experience. And let’s face it, Vercel makes deploying a snap, and super fast. I’ve also grown to like JSX, even though I didn’t initially. But that’s my opinion. You may prefer Angular or have a use-case where it’s a better fit than Next (Actually, Angular Universal is their full-stack framework, which is more comparable to Next.js). Good luck!
Thanks Tony for quick reply.
My advice is that since you are .net(c#) developer. There is no need of you learning node js for your backend. You can write your code on c# and convert it to other programming languages, there is and extension they use to do that but i have forgotten the name. Coming to react js and next js i will just say you should have it in mind that have to know atleast one frontend framework or library for your own benefits. Is not a compulsory that you will learn all, but when it comes in a situation you got job in a company that is using a new framework you’re new to, you have no option than to abide to their rules by forcing yourself to learn it because we learn in a work process. Is not a compulsory thing that you will be perfect on that framework before applying for that particular job.