Mapping JS Object properties to QProperties

I am trying to provide an object in JS, then use those in C++.

Code:

---

function GI(parent) {
QGraphicsItem.call(this, parent);
 this.myProp =1.0;
}
 
...
var item =  GI()
var anim = QPropertyAnimation (item, "myProp", null);
anim.setEndValue("myProp", 2);
anim.setDuration(10);
anim.start();

---

Also is there a way for me to tell which set*() functions were converted to properties *before* I get the debugger error?

TIA.