The primary use of the JavaScript programming language is to create interactive and dynamic content on websites. It enables developers to implement features like user interface enhancements, animations, and responsive design elements, enhancing overall user experience. JavaScript can also facilitate asynchronous communication with servers, allowing for dynamic updates without refreshing the page. As a core component of modern web technologies, including HTML and CSS, JavaScript is essential for developing interactive web applications and websites, making it one of the most widely-used programming languages.