storify.js

function storify(target = {}) {
    const observers = {},
          observables = {};
  
    return new Proxy(target, {
        get: function(target, property, receiver) {
            if (property in observables === false) {
                observables[property] = Rx.Observable.create(observer => {
                  observers[property] = observer;
                  
                  if (property in target) observer.next(target[property]);
                }).publishBehavior().refCount().skip(1);
            }
          
            return observables[property];
        },
      
        set: function(target, property, value, receiver) {
            target[property] = value;
            observers[property].next(value);
            return true;
        },
      
        deleteProperty: function(target, property) {
            if (delete target[property]) {
                observers[property].complete();
                delete observables[property];
                delete observers[property];
              
                return true;
            } else {
                return false;
            }
        }
    });
}

const s = storify();

const x = s.myvalue;

x.subscribe(x => console.log('xVal', x), x => console.log('xErr', x), x => console.log('xComp', x));

s.myvalue = 1;
// xVal 1
s.myvalue = 2;
// xVal 2
s.myvalue = 3;
// xVal 3
const y = s.myvalue;

y.subscribe(y => console.log('yVal', y), y => console.log('yErr', y), y => console.log('yComp', y));
// yVal 3
s.myvalue = 4;
// xVal 4
// yVal 4
s.myvalue = 5;
// xVal 4
// yVal 5
delete s.myvalue;
// xComp
// yComp