Question

I’m trying to understand how inheritance works in JS. Suppose we have a class:

Class = function () {
    this.A = 'A';
    this.B = 'B';
};

and we are trying to extend it

SubClass = function () {};
SubClass.prototype = new Class();

Do I understance correctly that after inheritance properties A and B are common for all instances of SubClass, since they belong to it’s prototype? If yes, how can Class be extended so that A and B do not be part of prototype?

UPD: note that Class uses A and B, so I can’t declare them in SubClass.

Thank you in advance!

Answer 1

All I want is to make A and B be accessible and specific for each
“instance”

The typical way of doing this is to pass parameters and assign them to properties. Then you can use call to reference the super class. In other words:

function Person( name, age ) {
  this.name = name;
  this.age = age;
}

function Student( name, age, grade ) {
  Person.call( this, name, age ); // call super-class with sub-class properties
  this.grade = grade;
}

Student.prototype = new Person();
Student.prototype.constructor = Student;

var roger = new Student( 'Roger', 18, 'A+' );