Yes, you can add ReactJS solutions to an already existing project. Initially, it was designed for gradual adoption, enabling a developer to add as many React pieces into the code as needed; most websites aren’t single-page apps and don’t have to be.
Technically, adding ReactJS to an existing project takes three steps: adding a DOM container to the HTML, inserting the script tags, and creating a React component. Provided that different web applications have unique infrastructures, it’s best to entrust this job to expert react JS development services.