As continuation to this question, i trying to add the respective json object name to infowindow content as,
 var infowindow = new google.maps.InfoWindow({
  content:i
  });
Which is given in this fiddle but it displays only the name of last object. I also tried with return function as
google.maps.event.addListener(poly, 'click', (function(event, (poly, i)) {
    return function() {
  infowindow.open(map);
  infowindow.setPosition(event.latLng);
    }
  })(poly, i)); 
but no use (fiddle). How can I achieve it?
                        
You said "But all brackets are correctly closed.". This is not correct (you have an extra set of parentheses in the function definition):
The
eventargument belongs to the returned function, and you only need closure on the polygon (poly) and the loop index (i):updated fiddle