Can ES6 class inheritance be translated into equivalent ES5 code?

Question

This answer shows how a simple ES6 class:

class A {
  constructor() {
    this.foo = 42;
  }

  bar() {
    console.log(this.foo);
  }
}

is equivalent the following ES5 code:

function A() {
  this.foo = 42;
}

A.prototype.bar = function() {
  console.log(this.foo);
}

Is is similarly possible to translate ES6 class inheritance to ES5 code? What would be the ES5 equivalent to following derived class?

class B extends A {
  constructor() {
    super();
    this.foo2 = 12;
  }

  bar() {
    console.log(this.foo + this.foo2);
  }

  baz() {
    console.log(this.foo - this.foo2);
  }
}

Answer 1

The equivalent in the sense of how it was done before (ignoring exact behaviours like property enumerability and extending actual ES6 classes from ES5-compatible code) was to:

• set the child prototype to a new object inheriting the parent prototype
• call the parent constructor from the child constructor

function B() {
  A.call(this);
  this.foo2 = 12;
}

B.prototype = Object.create(A.prototype);
B.prototype.constructor = B;

B.prototype.bar = function () {
  console.log(this.foo + this.foo2);
};

B.prototype.baz = function () {
  console.log(this.foo - this.foo2);
};

It was also possible to inherit properties of the constructor (“static”) using the de facto facility for modification of existing prototypes: B.__proto__ = A