Ignore old queries, remove highlight when beginning a new query.

select2.js

@@ -687,6 +687,7 @@ the specific language governing permissions and limitations under the Apache Lic
             this.results = results = this.container.find(resultsSelector);
             this.search = search = this.container.find("input.select2-input");
 
+            this.queryCount = 0;
             this.resultsPage = 0;
             this.context = null;
 
@@ -1412,7 +1413,7 @@ the specific language governing permissions and limitations under the Apache Lic
             if (index >= choices.length) index = choices.length - 1;
             if (index < 0) index = 0;
 
-            this.results.find(".select2-highlighted").removeClass("select2-highlighted");
+            this.removeHighlight();
 
             choice = $(choices[index]);
             choice.addClass("select2-highlighted");
@@ -1425,6 +1426,10 @@ the specific language governing permissions and limitations under the Apache Lic
             }
         },
 
+        removeHighlight: function() {
+            this.results.find(".select2-highlighted").removeClass("select2-highlighted");
+        },
+
         // abstract
         countSelectableResults: function() {
             return this.findHighlightableChoices().length;
@@ -1437,8 +1442,8 @@ the specific language governing permissions and limitations under the Apache Lic
                 var choices = this.findHighlightableChoices();
                 this.highlight(choices.index(el));
             } else if (el.length == 0) {
-                // if we are over an unselectable item remove al highlights
-                this.results.find(".select2-highlighted").removeClass("select2-highlighted");
+                // if we are over an unselectable item remove all highlights
+                this.removeHighlight();
             }
         },
 
@@ -1505,7 +1510,8 @@ the specific language governing permissions and limitations under the Apache Lic
                 self = this,
                 input,
                 term = search.val(),
-                lastTerm=$.data(this.container, "select2-last-term");
+                lastTerm = $.data(this.container, "select2-last-term"),
+                queryNumber;
 
             // prevent duplicate queries against the same term
             if (initial !== true && lastTerm && equal(term, lastTerm)) return;
@@ -1527,6 +1533,8 @@ the specific language governing permissions and limitations under the Apache Lic
                 postRender();
             }
 
+            queryNumber = ++this.queryCount;
+
             var maxSelSize = this.getMaximumSelectionSize();
             if (maxSelSize >=1) {
                 data = this.data();
@@ -1561,6 +1569,8 @@ the specific language governing permissions and limitations under the Apache Lic
 
             search.addClass("select2-active");
 
+            this.removeHighlight();
+
             // give the tokenizer a chance to pre-process the input
             input = this.tokenize();
             if (input != undefined && input != null) {
@@ -1578,6 +1588,11 @@ the specific language governing permissions and limitations under the Apache Lic
                     callback: this.bind(function (data) {
                 var def; // default choice
 
+                // ignore old responses
+                if (queryNumber != this.queryCount) {
+                  return;
+                }
+
                 // ignore a response if the select2 has been closed before it was received
                 if (!this.opened()) {
                     this.search.removeClass("select2-active");