What is the role of the `site.js` file in an SFCC project?

The role of the site.js file in an SFCC (Salesforce Commerce Cloud) project is to serve as the main entry point for client-side JavaScript code. This file is crucial because it allows developers to organize and initialize client-side scripts that will run in the browser. By using site.js, developers can control the overall behavior of the front-end of the application, ensuring that various interactive elements function as intended and enhancing the user experience on the site.

Client-side JavaScript is responsible for tasks such as manipulating the Document Object Model (DOM), handling events, and performing asynchronous operations (like AJAX calls). By centralizing this logic in the site.js file, it helps maintain structured and manageable code, which is especially important in larger projects.

Other options focus on responsibilities that are not aligned with the purpose of the site.js file. For instance, server-side logic and database interactions usually occur in different files or modules specific to the server (often in controllers or models), while user authentication is typically managed through dedicated security mechanisms or middleware, rather than being handled directly within a file like site.js.