bound-weakmap.js

const bindingsMap = new WeakMap();

function bound() {
  return (target, key, descriptor) => {
    const { enumerable, configurable, value } = descriptor;
    return {
      enumerable,
      configurable,
      get() {
        let bindings = bindingsMap.get(this);
        if (bindings === undefined) {
          bindings = {};
          bindingsMap.set(this, bindings);
        }
        let fn = bindings[key];
        if (fn === undefined) {
          bindings[key] = fn = value.bind(this);
          fn.orig = value;
        }
        return fn.orig === value ? fn : value;
      }
    }
  }
}

function applyDecorator(target, key, decorator) {
  let descriptor = Object.getOwnPropertyDescriptor(target, key);
  Object.defineProperty(target, key, decorator()(target, key, descriptor));
}

class A {
  perform(x) {
    console.log(`A.perform(${x})`);
  }
}

applyDecorator(A.prototype, 'perform', bound);

class B extends A {
  perform(x) {
    console.log(`B.perform(${x}) before`);
    super.perform(x);
    console.log(`B.perform(${x}) after`);
  }
}

applyDecorator(B.prototype, 'perform', bound);

const a = new A();
const b = new B();

const { perform: aPerform } = a;
const { perform: bPerform } = b;

bPerform(23);

bPerform(10);

aPerform(19);