var customFloatingObject = new GC.Spread.Sheets.FloatingObjects.FloatingObject("f1", 10, 10, 60, 64);
var btn = document.createElement('button');
btn.style.width = "60px";
btn.style.height = "30px";
btn.innerText = "button";
customFloatingObject.content(btn);
activeSheet.floatingObjects.add(customFloatingObject);
var customFloatingObject1 = new GC.Spread.Sheets.FloatingObjects.FloatingObject("f2", 10, 30, 60, 64);
var btn1 = document.createElement('button');
btn1.style.width = "50px";
btn1.style.height = "20px";
btn1.innerText = "test";
customFloatingObject1.content(btn1);
activeSheet.floatingObjects.add(customFloatingObject1);
alert(activeSheet.floatingObjects.zIndex("f1"));