I do not understand what ReactJs is for, I've seen several videos in some create components in a weird way for me but I do not understand what is useful, actually creating components would be the equivalent of creating an element in jQuery to click and to save something in the database without recharging the site, it is possible to do it with jQuery and Ajax for a long time, so what's the use?
Do you explain to me?
It's usually a normal doubt, Stackoverflow in English debates a bit more about the topic
I'm sorry to say that your question is prejudiced, reluctant to learn something new: Asking what ReactJs is for because we already have jQuery to do anything in javascript is like asking what is object-oriented programming for if we already had the programming imperative:
Frameworks and libraries like ReactJs, AngularJS, Angular, Aurelia, Ember ... are frameworks that allow you to create "Single Page Applications" (Applications on a single page) more efficiently than if you used the jQuery plugins, both in development time and in execution speed.