//This example uses the FloatingObjectRemoved event.
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);
activeSheet.bind(GC.Spread.Sheets.Events.FloatingObjectRemoved, function (e, info) {
        alert(info.sheetName);
});