What is the use of the ReactJS library?

The exact use of the ReactJS library is allowing the developers to build an intuitive user interface for a website or a mobile app. It is used to pay complete emphasis on user-friendly UI appeal to bring improved user experience.

Why ReactJS is not a framework?

ReactJS is not so good as a framework due to having so minimal functionalities. It deals little with the developer's zeal to learn more about the framework and falls short in terms of dealing with complex issues. However, as a library, ReactJS is extremely beneficial and extensively implemented by big brands across the globe.

Is ReactJS front-end or back-end?

Of course, ReactJS is a frontend development JavaScript-based library that is used by developers to create engaging UI. Since the user interface reflects at the front of any website or application, so library belongs to the frontend development part.