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():


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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();

Tarefa

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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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Seção 3. Capítulo 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();

Tarefa

Swipe to show code editor

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Tudo estava claro?

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Seção 3. Capítulo 1

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