I am unable to visualize how framework like Slim integrates with JS framework like React. Most projects that I came across in PHP world are based on some templating engine. Any link for sample project would be helpful to understand how a JS framework can be integrated with Slim and Twig templating engine.
FYI - I am a professional React developer with Java as backend.
These repos that make use of Slim Framework helped me gain some insights into building with Slim: