Module Definition Patterns (I)

The module system, besides being a mechanism for loading dependencies, is also a tool for defining APIs. Like any other problem related to API design, the main factor to consider is the balance between private and public functionality. The aim is to maximize information hiding and API usability, while balancing these with other software qualities, such as extensibility and code reuse.

In this section, we’ll analyze some of the most popular patterns for defining modules in Node.js, such as named exports, exporting functions, classes and instances, and monkey patching. Each one has its own balance of information hiding, extensibility, and code reuse.

Named exports

The most basic method for exposing a public API is using named exports, which involves assigning the values we want to make public to properties of the object referenced by exports (or module.exports). In this way, the resulting exported object becomes a container or namespace for a set of related functionalities.

The following code shows a module implementing this pattern: