Proxy the context of a class expression

class-constructor-proxy.js

// Thanks @BigAB

class Counter {
  constructor() {
    setTimeout(this.onTick.bind(this), 1000);
  }
  onTick() {
    const now = new Date();
    // want to call the set trap
    this.hours = now.getHours();
    // want to call the set trap
    this.minutes = now.getMinutes();
    // want to call the set trap
    this.seconds = now.getSeconds();
  }
}

function observeSets(instance) {
  const p = new Proxy(instance, {
    set(target, property, value, receiver) {
      console.log('SETTING', property, value);
      return Reflect.set(target, property, value, receiver);
    },
  });
  return p;
}

function proxyClass(ClassOrConstructor) {
  return new Proxy(ClassOrConstructor, {
    construct(target, argumentsList, newTarget) {
      return Reflect.construct(
        function() {
          const p = Object.create(target.prototype);
          const pp = observeSets(p);
          let instance = pp;
          instance = target.prototype.constructor.call(pp);
          return instance;
        },
        argumentsList,
        newTarget
      );
    },
  });
}

const ProxiedCounter = proxyClass(Counter);
const counter = new ProxiedCounter();