A React.js developer is a professional proficient in utilizing the React.js library for building dynamic and interactive user interfaces. React.js, developed by Facebook, is a JavaScript library widely used for front-end web development. React.js developers leverage components, a core concept in React, to create modular and reusable UI elements. They work with JSX (JavaScript XML) syntax to write components that efficiently update and render data-driven views. These developers possess a strong understanding of state management, virtual DOM (Document Object Model), and component lifecycle, ena