Javascript Classes - Constructor, Super, Extends and Static (Reference)

Tech:
Javascript
Since:
1 year ago
Views:
4

In Javascript, classes are a new feature that allows you to define a class and its methods. Some of the features of classes are Constructor, Super, Extends, Static.

constructor

The constructor is a special method that is called when a new instance of a class is created.It is used to initialize the newly created object.

class obj_constr {
  constructor(val) {
    this.aaa = val;
  }
}

var x = new obj_constr("aaa");
x.aaa;
// aaa

super

The super keyword is used to call the constructor of the parent class.

class obj_constr_1 {
  constructor(val_1) {
    this.aaa = val_1;
  }
}

class obj_constr_2 extends obj_constr_1 {
  constructor(val_1, val_2) {
    super(val_1);
    this.bbb = val_2;
  }
}

var x = new obj_constr_2("aaa", "bbb");
x.aaa;
// aaa

extends

The extends keyword is used to inherit the properties and methods of another class.

class obj_constr_1 {
  constructor(val_1) {
    this.aaa = val_1;
  }
  TEST1() {
    return this.aaa;
  }
}

class obj_constr_2 extends obj_constr_1 {
  constructor(val_1, val_2) {
    super(val_1);
    this.bbb = val_2;
  }
  TEST2() {
    return this.TEST1();
  }
}

var x = new obj_constr_2("aaa", "bbb");
x.TEST2();
// aaa

static

The static keyword is used to declare a static property. Static properties are properties that belong to the class instead of to instances of the class.

class obj_constr {
  constructor(val) {
    this.aaa = val;
  }
  static TEST() {
    // Code
  }
}

var x = new obj_constr("aaa");

obj_constr.TEST();
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