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.

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);


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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():

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();


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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

Swipe to start coding

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.

Solution

class Student{

name;

age;

gpa;

static ageOfMajority = 18;

static gpaLimit = 3.0;

constructor(name, age, gpa){

this.name = name;

this.age = age;

this.gpa = gpa;

console.log('Student created');

}

interview(){

if (this.gpa < Student.gpaLimit){

console.log('Assigned to the class B');

} else {

console.log('Assigned to the class A');

}

student = new Student('Robert', 22, 3.5);

student.interview();

Everything was clear?

Thanks for your feedback!

Section 3. Chapter 1

class Student{

name;

age;

gpa;

static ageOfMajority = 18;

constructor(name, age, gpa){

this.name = name;

this.age = age;

this.gpa = gpa;

console.log('Student created');

}

interview(){

}

student = new Student('Robert', 22, 3.5);

student.interview();