So all developer jobs need React or other framework now?

I have already applied for jobs for mouths already. I just noticed that almost all jobs said that they need the developers to have some front-end framework. I never worked with frontend frames before. When I got my last job there were still many jobs that just required the knowledge of a language and some kind of system design skills.

Since I never used any front-end framework except pure javascript, I want to ask a question:

What is the advice to build a what kind of project and use what kind of framework? I never worked as a front-end developer but seems now you must know these to get a job. What is the fastest way to get this knowledge and which kind of project is the best demo that I can put on my resume?