address @mrdoob comment: https://github.com/mrdoob/three.js/pull/6934#discussion_r36211920

src/animation/KeyframeTrack.js

@@ -107,7 +107,7 @@ THREE.KeyframeTrack.prototype = {
 	// sort in ascending order
 	sort: function() {
 
-		var keyComparator = function keyComparator(key0, key1) {
+		function keyComparator(key0, key1) {
 			return key0.time - key1.time;
 		};