Call static methods from regular ES6 class methods

Question

What\'s the standard way to call static methods? I can think of using constructor or using the name of the class itself, I don\'t like the latter since it doesn

Answer 1

I stumbled over this thread searching for answer to similar case. Basically all answers are found, but it's still hard to extract the essentials from them.

Kinds of Access

Assume a class Foo probably derived from some other class(es) with probably more classes derived from it.

Then accessing

• from static method/getter of Foo
  • some probably overridden static method/getter:
    • this.method()
    • this.property
  • some probably overridden instance method/getter:
    • impossible by design
  • own non-overridden static method/getter:
    • Foo.method()
    • Foo.property
  • own non-overridden instance method/getter:
    • impossible by design
• from instance method/getter of Foo
  • some probably overridden static method/getter:
    • this.constructor.method()
    • this.constructor.property
  • some probably overridden instance method/getter:
    • this.method()
    • this.property
  • own non-overridden static method/getter:
    • Foo.method()
    • Foo.property
  • own non-overridden instance method/getter:
    • not possible by intention unless using some workaround:
      • Foo.prototype.method.call( this )
      • Object.getOwnPropertyDescriptor( Foo.prototype,"property" ).get.call(this);

Keep in mind that using this isn't working this way when using arrow functions or invoking methods/getters explicitly bound to custom value.

Background

• When in context of an instance's method or getter
  • this is referring to current instance.
  • super is basically referring to same instance, but somewhat addressing methods and getters written in context of some class current one is extending (by using the prototype of Foo's prototype).
  • definition of instance's class used on creating it is available per this.constructor.
• When in context of a static method or getter there is no "current instance" by intention and so
  • this is available to refer to the definition of current class directly.
  • super is not referring to some instance either, but to static methods and getters written in context of some class current one is extending.

Conclusion

Try this code:

class A {
  constructor( input ) {
    this.loose = this.constructor.getResult( input );
    this.tight = A.getResult( input );
    console.log( this.scaledProperty, Object.getOwnPropertyDescriptor( A.prototype, "scaledProperty" ).get.call( this ) );
  }

  get scaledProperty() {
    return parseInt( this.loose ) * 100;
  }
  
  static getResult( input ) {
    return input * this.scale;
  }
  
  static get scale() {
    return 2;
  }
}

class B extends A {
  constructor( input ) {
    super( input );
    this.tight = B.getResult( input ) + " (of B)";
  }
  
  get scaledProperty() {
    return parseInt( this.loose ) * 10000;
  }

  static get scale() {
    return 4;
  }
}

class C extends B {
  constructor( input ) {
    super( input );
  }
  
  static get scale() {
    return 5;
  }
}

class D extends C {
  constructor( input ) {
    super( input );
  }
  
  static getResult( input ) {
    return super.getResult( input ) + " (overridden)";
  }
  
  static get scale() {
    return 10;
  }
}


let instanceA = new A( 4 );
console.log( "A.loose", instanceA.loose );
console.log( "A.tight", instanceA.tight );

let instanceB = new B( 4 );
console.log( "B.loose", instanceB.loose );
console.log( "B.tight", instanceB.tight );

let instanceC = new C( 4 );
console.log( "C.loose", instanceC.loose );
console.log( "C.tight", instanceC.tight );

let instanceD = new D( 4 );
console.log( "D.loose", instanceD.loose );
console.log( "D.tight", instanceD.tight );