Too Long; Didn't Read
This is the fourth part of SOLID Principles in JavaScript. In Javascript we have something similar to them, it's classes, but this principle could be applied to JS classes. It means that when we create a base class, we should declare all methods that will be used in subclasses and try to avoid methods, that some subclass will use, but some another subclass shouldn't use. This principle says: clients should not be forced to depend upon interfaces that they do not use. The "interface Segregation Principle" is about creating correct methods in the base class.