OpenLayers WFS Sum Attributed and loadend event

HTML

<script src="http://cdnjs.cloudflare.com/ajax/libs/openlayers/2.11/OpenLayers.js"></script>
<body onload="init()">
    <p>OpenLayers WFS with select control and Popups</p>
    <div id="map"></div>
</body>

CSS

#map {
    width: 400px;
    height: 600px;
}

JavaScript

var map;
var layer, wms, selectControl;

function init() {
    map = new OpenLayers.Map('map', {
    projection: "EPSG:25832",
    tileSize: new OpenLayers.Size(256, 256),
    units: "m",
    maxExtent: new OpenLayers.Bounds(120000, 5661139.2, 958860.8, 6500000),
    resolutions: [1638.4, 819.2, 409.6, 204.8, 102.4, 51.2, 25.6, 12.8, 6.4, 3.2, 1.6, 0.8, 0.4, 0.2]
});
    wms = new OpenLayers.Layer.WMS("Baggrundskort (FOT)", ["http://kortforsyningen.kms.dk/"], {
    servicename: "topo_fot",
    layers: "basis",
    format: "image/jpeg",
    login: "gmcb3",
    password: "3bcmg"
}, {
    isBaseLayer: true,
    buffer: 1,
    visibility: false,
    displayInLayerSwitcher: true
});

    layer = new OpenLayers.Layer.Vector("WFS", {

        strategies: [new OpenLayers.Strategy.BBOX()],
        protocol: new OpenLayers.Protocol.WFS({
            url: "http://wfs.gmpark.dk/wfs/albertslund/ows?service=WFS&typeName=albertslund:elements",
            featureType: "albertslund:elements",
            featureNS: "albertslund",
            srsName: "EPSG:25832",
        geometryName: "albertslund:geometry"
        })
    });

    layer.events.register("loadend", map, function () {
        console.log("number of Features: " + layer.features.length);

        var layer_sum = 0;
        for (var i = 0; i < layer.features.length; i++) {
            layer_sum = layer_sum + parseInt(layer.features[i].attributes.LABELRANK);
        }
        console.log(layer.features[0].attributes);
        console.log("Sum of attribute LABELRANK= " + layer_sum);

    });

    map.addLayers([wms, layer]);
    map.zoomToExtent(new OpenLayers.Bounds(708087, 6171295, 713490, 6178841));

    selectControl = new OpenLayers.Control.SelectFeature(map.layers[1], {
        onSelect: onFeatureSelect,
        onUnselect: onFeatureUnselect
    });

    map.addControl(selectControl);
    selectControl.activate();



}

function onPopupClose(evt) {
    selectControl.unselect(selectedFeature);
}

function...