Use ol.style.Style and construct style object once

examples/vector-layer.js

@@ -82,10 +82,7 @@ map.on('singleclick', function(evt) {
   displayFeatureInfo(pixel);
 });
 
-map.on('postcompose', function(evt) {
-  if (highlight) {
-    var render = evt.getRender();
-    render.drawFeature(highlight, {
+var highlightStyle = new ol.style.Style({
   stroke: new ol.style.Stroke({
     color: '#f00',
     width: 1
@@ -94,5 +91,10 @@ map.on('postcompose', function(evt) {
     color: 'rgba(255,0,0,0.1)'
   })
 });
+
+map.on('postcompose', function(evt) {
+  if (highlight) {
+    var render = evt.getRender();
+    render.drawFeature(highlight, highlightStyle);
   }
 });