why are my google maps event listeners not working properly?

问题

I'm trying to handle mouse over listener for each marker(there are 30 markers) and to show infowindows for these markers. I created listeners for each markers but when my mouse over the some marker it shows always the last marker's infowindows. To sum up I can't listen other markers. any help would be appreciated. thanks in advance and here my code :

var listeners = [];
for(var i = 0; i < markers.length; i++){
  var marker = markers[i];
  var contentString = contents[i];
  listeners[i] = new google.maps.event.addListener(marker, 'mouseover', function() {
    var hideInfoWindows = function(){
        for (var j = 0; j < util.Common.infowindows.length; j++) {
          util.Common.infowindows[j].close(); 
        }
    }
    var addInfoWindow = function(){
        var infowindow = new google.maps.InfoWindow({
            content: contentString
        });
        //hideInfoWindows();
        util.Common.infowindows.push(infowindow);
        infowindow.open(util.Common.googlemap,marker);
    }
    addInfoWindow();
  });
}

I'm also using js cluster library but I don't think the problem is related with it.

回答1:

I think your problem might be that you are not using a closure inside the cycle, and when the event listener is fired, the marker and the contentString variables are pointing to the last marker.

Try to rewrite the cycle like this:

var listeners = [];
for(var i = 0; i < markers.length; i++){
    (function(index){ //create a closure, variable 'index' will take its value from variable i, but won't be affected by changed i in the outer scope
        var marker = markers[index]; //use this scope's index variable instead of i
        var contentString = contents[index]; //use this scope's index variable instead of i
        listeners[index] = new google.maps.event.addListener(marker, 'mouseover', function() {
            var hideInfoWindows = function(){
                for (var j = 0; j < util.Common.infowindows.length; j++) {
                    util.Common.infowindows[j].close();
                }
            };
            var addInfoWindow = function(){
                var infowindow = new google.maps.InfoWindow({
                    content: contentString
                });
                //hideInfoWindows();
                util.Common.infowindows.push(infowindow);
                infowindow.open(util.Common.googlemap,marker);
            };
            addInfoWindow();
        });
    })(i);
}

来源：https://stackoverflow.com/questions/31983445/why-are-my-google-maps-event-listeners-not-working-properly