wrapApplier.js

{// scoped

class A {
  a () { return 1 }
}

// wraps existing function
function baseWrapApplier(theConstructor, appliyingKey, descriptor) {
  if (theConstructor.prototype[appliyingKey]) {

  }
  return function WrapApplierConstructor(constructorArgs) {
    const obj = Object.create(theConstructor.prototype)
    return Object.defineProperty(obj, appliyingKey, descriptor)
  }
}

function wrapApplier(theConstructor, appliyingKey, value) {
  return baseWrapApplier(theConstructor, appliyingKey, { value })
}

const A2 = wrapApplier(A, 'a', function a(){ return 2; })

const a = new A2
console.log(a.a())
console.assert(a.a() === 2, 'Failed: value is', a.a())

}