Course Content

Object-Oriented Programming in JavaScript

1. Classes & Objects

Classes Class Attributes Class Methods Objects' Creating Keyword 'this'Constructor

2. Encapsulation

Private Modifier Get and Set

3. Static

Static Attributes Static Functions

4. Inheritance

What is an Inheritance Constructor Inheritance Overriding

Static Attributes

As you already know, each object can have a unique attribute value, like, for example, studentA has name Andrew and studentB has name William. But sometimes it makes sense to set some static value - the common for all instances of the class.

Let's add a attribute called ageOfMajority. Obviously, the value is 18 for all Students’ objects, and can't be different for different students. We’ll add a static keyword.


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class Student{
  name;
  age;
  static ageOfMajority = 18
  constructor(name, age){
    this.name = name;
    this.age = age;
    console.log('Student created');
  }
}

student = new Student('Robert', 22);

console.log(Student.ageOfMajority);

To refer to the static attribute, use the name of the class, not the object, because it is a property of the class.

Inside non-static functions, you can refer static attribute only using class name, not this keyword. Look how we refer non-static age and static ageOfMajority in method drink():


              123456789101112131415161718192021
            
class Student{
  name;
  age;
  static ageOfMajority = 18;
  constructor(name, age){
    this.name = name;
    this.age = age;
    console.log('Student created');
  }
  drink(){
    if (this.age < Student.ageOfMajority){
      console.log('I am too young, only', this.age, 'yrs old.');
    } else {
      console.log('I am drunk.');
    }
  }
}

student = new Student('Robert', 22);

student.drink();

Task

Let's create function interview(), which assigns a student to the class A, if GPA >= 3.0, or class B if not. For this, define static attribute gpaLimit and assign it with 3.0, and inside interview() function compare it with student's GPA. Print message Assigned to the class A or Assigned to the class B.

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Everything was clear?

Thanks for your feedback!

Section 3. Chapter 1

Static Attributes

Let's add a attribute called ageOfMajority. Obviously, the value is 18 for all Students’ objects, and can't be different for different students. We’ll add a static keyword.


              1234567891011121314
            
class Student{
  name;
  age;
  static ageOfMajority = 18
  constructor(name, age){
    this.name = name;
    this.age = age;
    console.log('Student created');
  }
}

student = new Student('Robert', 22);

console.log(Student.ageOfMajority);

To refer to the static attribute, use the name of the class, not the object, because it is a property of the class.

Inside non-static functions, you can refer static attribute only using class name, not this keyword. Look how we refer non-static age and static ageOfMajority in method drink():


              123456789101112131415161718192021
            
class Student{
  name;
  age;
  static ageOfMajority = 18;
  constructor(name, age){
    this.name = name;
    this.age = age;
    console.log('Student created');
  }
  drink(){
    if (this.age < Student.ageOfMajority){
      console.log('I am too young, only', this.age, 'yrs old.');
    } else {
      console.log('I am drunk.');
    }
  }
}

student = new Student('Robert', 22);

student.drink();

Task

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Thanks for your feedback!

Section 3. Chapter 1

Static Attributes

Let's add a attribute called ageOfMajority. Obviously, the value is 18 for all Students’ objects, and can't be different for different students. We’ll add a static keyword.


              1234567891011121314
            
class Student{
  name;
  age;
  static ageOfMajority = 18
  constructor(name, age){
    this.name = name;
    this.age = age;
    console.log('Student created');
  }
}

student = new Student('Robert', 22);

console.log(Student.ageOfMajority);

To refer to the static attribute, use the name of the class, not the object, because it is a property of the class.

Inside non-static functions, you can refer static attribute only using class name, not this keyword. Look how we refer non-static age and static ageOfMajority in method drink():


              123456789101112131415161718192021
            
class Student{
  name;
  age;
  static ageOfMajority = 18;
  constructor(name, age){
    this.name = name;
    this.age = age;
    console.log('Student created');
  }
  drink(){
    if (this.age < Student.ageOfMajority){
      console.log('I am too young, only', this.age, 'yrs old.');
    } else {
      console.log('I am drunk.');
    }
  }
}

student = new Student('Robert', 22);

student.drink();

Task

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Thanks for your feedback!

Let's add a attribute called ageOfMajority. Obviously, the value is 18 for all Students’ objects, and can't be different for different students. We’ll add a static keyword.


              1234567891011121314
            
class Student{
  name;
  age;
  static ageOfMajority = 18
  constructor(name, age){
    this.name = name;
    this.age = age;
    console.log('Student created');
  }
}

student = new Student('Robert', 22);

console.log(Student.ageOfMajority);

To refer to the static attribute, use the name of the class, not the object, because it is a property of the class.

Inside non-static functions, you can refer static attribute only using class name, not this keyword. Look how we refer non-static age and static ageOfMajority in method drink():


              123456789101112131415161718192021
            
class Student{
  name;
  age;
  static ageOfMajority = 18;
  constructor(name, age){
    this.name = name;
    this.age = age;
    console.log('Student created');
  }
  drink(){
    if (this.age < Student.ageOfMajority){
      console.log('I am too young, only', this.age, 'yrs old.');
    } else {
      console.log('I am drunk.');
    }
  }
}

student = new Student('Robert', 22);

student.drink();

Task

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Section 3. Chapter 1

Switch to desktop for real-world practiceContinue from where you are using one of the options below