OpenLayers: changing feature's style.

Shows switch of an image of a feature every two seconds.

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/openlayers/2.13.1/lib/OpenLayers.js"></script>
<div id="mapdiv"></div>

CSS

#mapdiv {
  width: 500px;
  height: 500px;
  border: 1px solid #dddddd;
}

JavaScript

var map = new OpenLayers.Map("mapdiv", {
  controls: [
    new OpenLayers.Control.Navigation(),
    new OpenLayers.Control.PanZoom(),
  ]
});

var baseAerial = new OpenLayers.Layer.OSM("MapQuest Open Aerial Tiles", null, {});
map.addLayer(baseAerial);

var vectorLayer = new OpenLayers.Layer.Vector("Vector");
var feature = new OpenLayers.Feature.Vector(
  new OpenLayers.Geometry.Point(44, 55), {}, {
    externalGraphic: 'http://www.gatesms.eu/img/loga/java.png',
    graphicHeight: 30,
    graphicWidth: 30
  });
vectorLayer.addFeatures([feature]);
map.addLayer(vectorLayer);
map.zoomToMaxExtent();

var switcher = true;

function imageSwitch() {
  if (switcher) feature.style.externalGraphic = 'http://blog.tiger.com.pl/wp-content/uploads/2012/02/Duke256.png';
  else feature.style.externalGraphic = 'http://www.gatesms.eu/img/loga/java.png';
  feature.layer.drawFeature(feature);
  switcher = !switcher;
  setTimeout(imageSwitch, 2000);
}
setTimeout(imageSwitch, 2000);