A JavaScript Developer is responsible for building and maintaining interactive web applications, ensuring seamless user experiences through dynamic and responsive design. They work with frameworks like React, Vue.js, or Angular to develop front-end components and integrate APIs. Strong problem-solving skills, expertise in modern JavaScript (ES6+), and a keen eye for UI/UX principles are essential. Collaboration with designers and back-end developers is crucial to delivering scalable, efficient, and high-performance web solutions.