Google Maps: Auto close open InfoWindows?

alternative solution for this with using many infowindows: save prev opened infowindow in a variable and then close it when new window opened

var prev_infowindow =false; 
...
base.attachInfo = function(marker, i){
    var infowindow = new google.maps.InfoWindow({
        content: 'yourmarkerinfocontent'
    });

    google.maps.event.addListener(marker, 'click', function(){
        if( prev_infowindow ) {
           prev_infowindow.close();
        }

        prev_infowindow = infowindow;
        infowindow.open(base.map, marker);
    });
}

There is a close() function for InfoWindows. Just keep track of the last opened window, and call the close function on it when a new window is created.