function vs. class constructor for a library

initClass.js

module.exports = class {
  constructor (foo) {
    class A {
      constructor (a) {
        this.a = foo(a);
      }
    }

    class B {
      constructor (b) {
        this.b = foo(b);
      }
    }

    return {A, B}
  }
}

initClass2.js

module.exports = class {
  constructor (foo) {
    class A {
      constructor (a) {
        this.a = foo(a);
      }
    }

    class B {
      constructor (b) {
        this.b = foo(b);
      }
    }

    this.ret = {A, B}
  }

  doIt () { return this.ret; }
}

initFunc.js

module.exports = (foo) => {
  class A {
    constructor (a) {
      this.a = foo(a);
    }
  }

  class B {
    constructor (b) {
      this.b = foo(b);
    }
  }

  return {A, B}
}

toy.js

const Func = require('./initFunc')(MyFoo)
const Clas = new (require('./initClass'))(MyFoo)

console.warn('Func', new Func.A(1).a)
console.warn('Func', new Func.B('b').b)
console.warn('Clas', new Clas.A(2).a)
console.warn('Clas', new Clas.B('d').b)

function MyFoo (x) {
  return x + x
}