Depth of the inheritance tree (DIT)

We can also declare a new class that inherits from a class, which is already inheriting from another class. In the following code snippet, we declare a class called SchoolPrincipal that extends the Teacher class, which extends the Person class:

class SchoolPrincipal extends Teacher { 
    public manageTeachers() { 
        return console.log( 
            `We need to help our students!` 
        ); 
    } 
} 

If we create an instance of the SchoolPrincipal class, we will be able to access all the properties and methods from its parent classes (SchoolPrincipal, Teacher, and Person):

const principal = new SchoolPrincipal( 
    "Remo", 
    "Jansen", 
    "remo.jansen@wolksoftware.com" 
); 
 
principal.greet(); // "Hi!" 
principal.teach(); // "Welcome to class!" 
principal.manageTeachers(); // "We need to help our students!" 

Unfortunately, we don't have a specific rule that we can follow when we are unsure whether we should increase the depth of the inheritance tree (DIT).

We should use inheritance in such a way that it helps us to reduce the complexity of our application and not the opposite. We should try to keep the DIT between zero and four because a value greater than four would compromise encapsulation and increase complexity.