A JS . developer utilizes the JavaScript programming language to build, maintain, and improve websites or web applications. They design user-friendly interfaces, implement responsive design, and ensure optimal performance. They collaborate with other developers, designers, and clients to create and enhance functionalities. They also debug and troubleshoot code, integrate third-party services, and optimize applications for maximum speed and scalability. Additionally, they use modern JavaScript frameworks like React or Vue.js, handle server-side logic, and manage data storage solutions. They also ensure all code is valid, properly structured, meets industry standards, and is compatible with browsers or devices.