Виртуальный метод при композиции

class A { 
  constructor() { 
    this.x = 'A'; 
    this.a = 'a'; 
  } 
   
  getOuter() { 
    console.log('outer'); 
    return `(${this.getInner()})`; 
  } 
   
  getInner() { 
    console.log('a'); 
    return this.x + this.a; 
  } 
} 
 
var a = new A 
 
class Wrapper { 
  constructor(original) { 
    this.original = original 
  } 
   
  getOuter() { 
    this.original.getInner = this.getInner.bind(this); 
    return this.original.getOuter(); 
  } 
   
  getInner() { 
    delete this.original.getInner; 
    return this.original.getInner(); 
  } 
} 
 
class B extends Wrapper { 
  constructor(original) { 
    super(original); 
    this.x = 'B'; 
    this.b = 'b'; 
  } 
   
  getInner() { 
    console.log('b'); 
    return `[${this.x}${this.b}][${super.getInner()}]`; 
  } 
} 
 
var b = new B(a); 
 
class C extends Wrapper { 
  constructor(original) { 
    super(original); 
    this.x = 'C'; 
    this.c = 'c'; 
  } 
   
  getInner() { 
    console.log('c'); 
    return `<${this.x}${this.c}><${super.getInner()}>`; 
  } 
} 
 
var c = new C(b); 
 
console.log(c.getOuter());