Describe the function of JavaScript libraries.

The function of JavaScript libraries is to simplify complex tasks by providing pre-written code for common functionalities. These libraries encompass a collection of JavaScript functions that streamline many programming processes, allowing developers to avoid the repetitive task of writing code from scratch for tasks that are frequently encountered in web development.

For example, libraries like jQuery enable developers to easily manipulate the Document Object Model (DOM), handle events, and make AJAX calls with very little code, which significantly enhances productivity. This convenience allows developers to focus more on application logic and user experience rather than on the intricacies of everyday coding tasks.

Other options, while relevant to web development, do not accurately capture the primary purpose of JavaScript libraries. Enhancing CSS styling pertains to CSS frameworks rather than JavaScript libraries. Managing server-side scripts is typically handled by server-side programming languages like PHP, Python, or Node.js, and does not involve JavaScript libraries directly. Compiling HTML code is also outside the function of JavaScript libraries, as HTML is a markup language that does not require compilation in the way programming languages like Java do. Thus, the correct answer highlights the essential role of JavaScript libraries in simplifying development processes through their pre-written code solutions.