What is the purpose of including a separate es.js file in a Liferay theme?

Including a separate es.js file in a Liferay theme serves the purpose of utilizing ECMAScript features in Metal.js. This file is designed to allow developers to write modern JavaScript using ES6+ specifications while working within the Liferay framework. By leveraging ECMAScript features, such as modules, arrow functions, classes, and template literals, developers can create more efficient, cleaner, and maintainable code.

Metal.js, the base framework used in Liferay for front-end development, enables support for these modern JavaScript features. By isolating the ES6 code in a separate file, developers can take advantage of enhanced JavaScript capabilities without compromising the compatibility and functionality of the overall Liferay theme.

The other options focus on different aspects of theme development; layout templates pertain to the structural design of pages, CSS customizations relate to styling, and managing theme settings involves configurations. However, these do not directly relate to utilizing ECMAScript features, which is the specific purpose of having an es.js file in a Liferay theme.