Mastering JavaScript Design Patterns - Second Edition

Decorator

The decorator pattern is used to wrap and augment an existing class. Using a decorator pattern is an alternative to subclassing an existing component. Subclassing is typically a compile time operation and is a tight coupling. This means that once subclassing is performed, there is no way to alter it at runtime. In cases where there are many possible subclassings that can act in combination, the number of combinations of subclassings explodes. Let's look at an example.

The armor worn by knights in Westeros can be quite configurable. Armor can be fabricated in a number of different styles: scale, lamellar, chainmail, and so on. In addition to the style of armor, there is also a variety of different face guards, knee, and elbow joints, and, ...