What is the correct way to add ECMAScript code to a theme's main.js?

To properly include ECMAScript code in a theme's main.js file, using a require statement is the most effective and common practice within the Liferay framework. This method leverages Liferay’s module loading system, which allows for the organized inclusion of dependencies, making the code modular and easier to manage.

When you use a require statement, you can load other JavaScript modules or libraries that your script depends on. This helps maintain a clean architecture, avoids polluting the global namespace, and can improve loading performance because the required modules will be loaded only as needed. It ensures that the main.js file can focus on the theme's specific functionality while relying on external scripts only when necessary.

Including comments, while useful for documentation, does not add functional code to your theme. Similarly, referencing an external library might indicate where external resources can be utilized, but it won't directly integrate your custom JavaScript logic into your main.js file. Using a JSON file does not apply to adding JavaScript code, as JSON serves as a data interchange format rather than a scripting language. Therefore, the most effective approach in this context is indeed using a require statement to effectively manage dependencies and maintain clear organization within your scripts.