JavaScript is a high-level, dynamic, interpreted programming language widely utilized in web development. Its primary function is to enable client-side interactivity, allowing web browsers to execute scripts that modify the Document Object Model (DOM) and handle user interactions without requiring constant communication with the server. Beyond the browser, the language has expanded into a server-side scripting capability through specialized runtime environments. This versatility allows it to power full-stack applications, facilitating tasks such as building complex Single Page Applications, creating backend APIs, and managing real-time data streaming, making it one of the most prevalent languages in modern computing infrastructure.