Proxy observable

function makeObservable(target) {

  let handler;

  target.observe = function(handler1){
    handler = handler1;
  };
  
  let proxy = new Proxy(target,{
    set(target,prop,val){
      handler(prop,val);
      return Reflect.set(target,prop,val);
    }    
  });
 
  
  return proxy;
}

let user = {};
user = makeObservable(user);

user.observe((key, value) => {
  console.log(`SET ${key}=${value}`);
});

user.name = "John"; // alerts: SET name=John
user.age =34;