Mastering JavaScript Design Patterns - Second Edition

Visitor

The final pattern in this section is the visitor pattern. The visitor provides a method of decoupling an algorithm from the object structure on which it operates. If we wanted to perform some action over a collection of objects which differ in type and we want to perform a different action depending on the object type, we would typically need to make use of a large if statement.

Let's get right into an example of this in Westeros. An army is made up of a few different classes of fighting person (it is important that we be politically correct as there are many notable female fighters in Westeros). However, each member of the army implements a hypothetical interface called IMemberOfArmy:

interface IMemberOfArmy{
  printName();
}

A simple implementation ...