You have to learn the architecture of the full stack ( Frontend & backend ) and how to connect with each other. When you grasp the You have to learn the architecture of the full stack ( Frontend & backend ) and how to connect with each other. When you grasp the architecture you can build any full-stackYou have to learn the architecture of the full stack ( Frontend & backend ) and how to connect with each other. When you grasp the You have to learn the architecture of the full stack ( Frontend & backend ) and how to connect with each other. When you grasp the architecture you can build any full stack js app whatever the framework. However the most popular is MERN but express.js is not maintained currently. I would recommend Fastify.js for the backend.