DOM property watcher using ES6 proxies.

dom-property-watcher.js

// Watch accesses/sets on a DOM element property.
function watchPropsOn(el) {
  return new Proxy(el, {
    get(target, propKey, receiver) {
      //return Reflect.get(target, propKey, receiver);
            console.log('get', propKey);
      return el[propKey];
    },
    set(target, propKey, value, receiver) {
      console.log('set', propKey, value);
      target[propKey] = value;
    }
  });
}

let el = document.createElement('div');

let elProxy = watchPropsOn(el);
elProxy.textContent = 'hi there';
console.log(elProxy.textContent);

function can watch properties, but ignores setAttribute() to change attributes / properties and fails with method calls!
Error message for "setAttribute" call:

get setAttribute
VM20409:1 Uncaught TypeError: Illegal invocation
    at <anonymous>:1:7

Could be handled by get handler like that.

function watchPropsOn(el) {
                return new Proxy(el, {
                    get(target, propKey, receiver) {
                    console.log('get', propKey);
                    return el[propKey].call ? (...args) => el[propKey](...args) : el[propKey];  // proxy methods if callable, else return property
                    },
                    set(target, propKey, value, receiver) {
                    console.log('set', propKey, value);
                    target[propKey] = value;
                    }
                });
            }