Google API：无法在地图上隐藏标记

Question

我编写了一部分代码，用于在Google地图上放置迭代标记：

   var markers = [];
   var coordinates = [];
   var interest_points = [];
   var joined_data = [];
   var map = null;
   var key_obj = new Map();
   var markers = [];
   var directionsDisplay = [];
   var directionsService = new google.maps.DirectionsService();
   var REQUEST_WAYPOINTS_LIMIT = 8;

    function placeMarker(lat, lon, icon_path)
    {
        var markerPos = new google.maps.LatLng(lat, lon);
        var marker = new google.maps.Marker
        (
            {
                position: markerPos,
                map: map,
                //animation: google.maps.Animation.DROP,
                icon: icon_path
            }
        );

        markers.push(marker);
    }

    function placeAttractionMarker(lat, lon, icon_path, name, url, id)
    {

        var contentString = '<div id="content"><div id="siteNotice">' +
            '</div><div id="bodyContent"><h4 id="firstHeading" class="firstHeading">' +  name + '</h4>' +
            '<a href="' + url + '" style="text-decoration:none" target="_blank"><b>Sito web</b></a></br>' +
            '<a href="" onclick="addMarkerToWps(this.id)" id="' + id +
            '">Aggiungi attrazione al percorso</a></div></div>';


        var infowindow = new google.maps.InfoWindow({
            content: contentString
        });

        var markerPos = new google.maps.LatLng(lat, lon);
        var marker = new google.maps.Marker
        (
            {
                position: markerPos,
                map: map,
                //animation: google.maps.Animation.DROP,
                icon: icon_path,
                title: name
            }
        );

        marker.addListener('click', function() {
            infowindow.open(map, marker);
        });

        markers.push(marker);
    }

我使用了两种不同的功能，因为我需要放置两种不同的标记。从代码中可以看出，某些标记在单击时会显示气球。在气球内部，有一个URL链接，我只需要在点击链接时启动功能 addMarkerToWps ：

function setMapOnAll(map_name) {
    for (var i = 0; i < markers.length; i++) {
        markers[i].setMap(map_name);
    }

    //markers = [];
}



function addMarkerToWps(wp_id)
{
    setMapOnAll(null);
}

无论如何标记都不会消失，即使看起来地图已重新加载。

编辑：放置标记并在地图上计算路径的函数

function calculateRoutes(reDraw)
{
    // remove previous route
    removeRoutes();
    //window.alert('Numero punti ' + coordinates.length);

    // set start position
    //var begin = new google.maps.LatLng(coordinates[0].Lat, coordinates[0].Lon);
    var begin = new google.maps.LatLng(joined_data[0].Lat, joined_data[0].Lon);

    // set end position
    var end = null;

    // waypoints struct
    var waypoints = [];

    // counter
    var wCount = 0;

    // loop
    var i;
    //for(i=1; i<coordinates.length-1; i++)
    for(i=1; i<joined_data.length-1; i++)
    {
        if(wCount === REQUEST_WAYPOINTS_LIMIT)
        {
            // increment counter to get end's index
            i++;

            // set end
            //end = new google.maps.LatLng(coordinates[i].Lat, coordinates[i].Lon);
            end = new google.maps.LatLng(joined_data[i].Lat, joined_data[i].Lon);

            // draw current route
            drawRoute(begin, end, waypoints);

            // update indeces
            begin = end;

            // reset structures
            wCount = 0;
            waypoints = [];
        }

        // add waypoint to list
        waypoints.push
        (
            {
                //location: new google.maps.LatLng(coordinates[i].Lat, coordinates[i].Lon),
                location: new google.maps.LatLng(joined_data[i].Lat, joined_data[i].Lon),
                stopover: true
            }
        );

        // increments counter
        wCount++;
    }

    if(waypoints.length > 0)
    {
        //end = new google.maps.LatLng(coordinates[coordinates.length-1].Lat, coordinates[coordinates.length-1].Lon);
        end = new google.maps.LatLng(joined_data[joined_data.length-1].Lat, joined_data[joined_data.length-1].Lon);
        drawRoute(begin, end, waypoints);
    }

    if(!reDraw)
    {
        for(var i = 0; i<coordinates.length; i++)
        {
            placeMarker(coordinates[i].Lat, coordinates[i].Lon, "http://gmaps-samples.googlecode.com/svn/trunk/markers/red/blank.png");
        }

        for(var j = 0; j<interest_points.length; j++)
        {
            placeAttractionMarker(
                interest_points[j].Lat,
                interest_points[j].Lon,
                "http://gmaps-samples.googlecode.com/svn/trunk/markers/orange/blank.png",
                interest_points[j].Name,
                interest_points[j].Wikipedia,
                j

            );
        }
    }

    else
    {
        for(var i = 0; i<coordinates.length; i++)
        {
            placeMarker(coordinates[i].Lat, coordinates[i].Lon, "http://gmaps-samples.googlecode.com/svn/trunk/markers/red/blank.png");
        }

        key_obj.forEach(function(value, key) {
            console.log(key + " = ");
        }, key_obj)
    }

你能告诉我为什么吗？

由于