Improve jQuery performance issues

This improves a regression added in b9b55cec4403f69d999ff6c3b90472805dfbed71
that reduced performance for large number of options when using a
jQuery collection object to append multiple options instead of
using a bare array containing the jQuery elements.

As `$.fn.add` is only required for jQuery 1.7.x, we can use a
utility function that only falls back to it for that specific
version of jQuery, and uses `$.fn.append` with an array for all
other versions.

This closes https://github.com/select2/select2/issues/3230.

dist/js/select2.full.js

@@ -714,6 +714,23 @@ S2.define('select2/utils',[
     });
   };
 
+  // Append an array of jQuery nodes to a given element.
+  Utils.appendMany = function ($element, $nodes) {
+    // jQuery 1.7.x does not support $.fn.append() with an array
+    // Fall back to a jQuery object collection using $.fn.add()
+    if ($.fn.jquery.substr(0, 3) === '1.7') {
+      var $jqNodes = $();
+
+      $.map($nodes, function (node) {
+        $jqNodes = $jqNodes.add(node);
+      });
+
+      $nodes = $jqNodes;
+    }
+
+    $element.append($nodes);
+  };
+
   return Utils;
 });
 
@@ -1565,7 +1582,7 @@ S2.define('select2/selection/multiple',[
       return;
     }
 
-    var $selections = $();
+    var $selections = [];
 
     for (var d = 0; d < data.length; d++) {
       var selection = data[d];
@@ -1578,10 +1595,12 @@ S2.define('select2/selection/multiple',[
 
       $selection.data('data', selection);
 
-      $selections = $selections.add($selection);
+      $selections.push($selection);
     }
 
-    this.$selection.find('.select2-selection__rendered').append($selections);
+    var $rendered = this.$selection.find('.select2-selection__rendered');
+
+    Utils.appendMany($rendered, $selections);
   };
 
   return MultipleSelection;
@@ -3015,7 +3034,7 @@ S2.define('select2/data/select',[
   };
 
   SelectAdapter.prototype.addOptions = function ($options) {
-    this.$element.append($options);
+    Utils.appendMany(this.$element, $options);
   };
 
   SelectAdapter.prototype.option = function (data) {
@@ -3185,7 +3204,7 @@ S2.define('select2/data/array',[
       return self.item($(this)).id;
     }).get();
 
-    var $options = $();
+    var $options = [];
 
     // Filter out all items except for the one passed in the argument
     function onlyItem (item) {
@@ -3216,10 +3235,10 @@ S2.define('select2/data/array',[
       if (item.children) {
         var $children = this.convertToOptions(item.children);
 
-        $option.append($children);
+        Utils.appendMany($option, $children);
       }
 
-      $options = $options.add($option);
+      $options.push($option);
     }
 
     return $options;
@@ -3403,7 +3422,7 @@ S2.define('select2/data/tags',[
         var $option = self.option(tag);
         $option.attr('data-select2-tag', true);
 
-        self.addOptions($option);
+        self.addOptions([$option]);
 
         self.insertTag(data, tag);
       }
@@ -5468,8 +5487,8 @@ S2.define('select2/compat/inputData',[
   };
 
   InputData.prototype.addOptions = function (_, $options) {
-    var options = $.map($options, function (option) {
-      return $.data(option, 'data');
+    var options = $.map($options, function ($option) {
+      return $.data($option[0], 'data');
     });
 
     this._currentData.push.apply(this._currentData, options);

dist/js/select2.js

@@ -714,6 +714,23 @@ S2.define('select2/utils',[
     });
   };
 
+  // Append an array of jQuery nodes to a given element.
+  Utils.appendMany = function ($element, $nodes) {
+    // jQuery 1.7.x does not support $.fn.append() with an array
+    // Fall back to a jQuery object collection using $.fn.add()
+    if ($.fn.jquery.substr(0, 3) === '1.7') {
+      var $jqNodes = $();
+
+      $.map($nodes, function (node) {
+        $jqNodes = $jqNodes.add(node);
+      });
+
+      $nodes = $jqNodes;
+    }
+
+    $element.append($nodes);
+  };
+
   return Utils;
 });
 
@@ -1565,7 +1582,7 @@ S2.define('select2/selection/multiple',[
       return;
     }
 
-    var $selections = $();
+    var $selections = [];
 
     for (var d = 0; d < data.length; d++) {
       var selection = data[d];
@@ -1578,10 +1595,12 @@ S2.define('select2/selection/multiple',[
 
       $selection.data('data', selection);
 
-      $selections = $selections.add($selection);
+      $selections.push($selection);
     }
 
-    this.$selection.find('.select2-selection__rendered').append($selections);
+    var $rendered = this.$selection.find('.select2-selection__rendered');
+
+    Utils.appendMany($rendered, $selections);
   };
 
   return MultipleSelection;
@@ -3015,7 +3034,7 @@ S2.define('select2/data/select',[
   };
 
   SelectAdapter.prototype.addOptions = function ($options) {
-    this.$element.append($options);
+    Utils.appendMany(this.$element, $options);
   };
 
   SelectAdapter.prototype.option = function (data) {
@@ -3185,7 +3204,7 @@ S2.define('select2/data/array',[
       return self.item($(this)).id;
     }).get();
 
-    var $options = $();
+    var $options = [];
 
     // Filter out all items except for the one passed in the argument
     function onlyItem (item) {
@@ -3216,10 +3235,10 @@ S2.define('select2/data/array',[
       if (item.children) {
         var $children = this.convertToOptions(item.children);
 
-        $option.append($children);
+        Utils.appendMany($option, $children);
       }
 
-      $options = $options.add($option);
+      $options.push($option);
     }
 
     return $options;
@@ -3403,7 +3422,7 @@ S2.define('select2/data/tags',[
         var $option = self.option(tag);
         $option.attr('data-select2-tag', true);
 
-        self.addOptions($option);
+        self.addOptions([$option]);
 
         self.insertTag(data, tag);
       }

src/js/select2/compat/inputData.js

@@ -116,8 +116,8 @@ define([
   };
 
   InputData.prototype.addOptions = function (_, $options) {
-    var options = $.map($options, function (option) {
-      return $.data(option, 'data');
+    var options = $.map($options, function ($option) {
+      return $.data($option[0], 'data');
     });
 
     this._currentData.push.apply(this._currentData, options);

src/js/select2/data/array.js

@@ -35,7 +35,7 @@ define([
       return self.item($(this)).id;
     }).get();
 
-    var $options = $();
+    var $options = [];
 
     // Filter out all items except for the one passed in the argument
     function onlyItem (item) {
@@ -66,10 +66,10 @@ define([
       if (item.children) {
         var $children = this.convertToOptions(item.children);
 
-        $option.append($children);
+        Utils.appendMany($option, $children);
       }
 
-      $options = $options.add($option);
+      $options.push($option);
     }
 
     return $options;

src/js/select2/data/select.js

@@ -151,7 +151,7 @@ define([
   };
 
   SelectAdapter.prototype.addOptions = function ($options) {
-    this.$element.append($options);
+    Utils.appendMany(this.$element, $options);
   };
 
   SelectAdapter.prototype.option = function (data) {

src/js/select2/data/tags.js

@@ -71,7 +71,7 @@ define([
         var $option = self.option(tag);
         $option.attr('data-select2-tag', true);
 
-        self.addOptions($option);
+        self.addOptions([$option]);
 
         self.insertTag(data, tag);
       }

src/js/select2/selection/multiple.js

@@ -76,7 +76,7 @@ define([
       return;
     }
 
-    var $selections = $();
+    var $selections = [];
 
     for (var d = 0; d < data.length; d++) {
       var selection = data[d];
@@ -89,10 +89,12 @@ define([
 
       $selection.data('data', selection);
 
-      $selections = $selections.add($selection);
+      $selections.push($selection);
     }
 
-    this.$selection.find('.select2-selection__rendered').append($selections);
+    var $rendered = this.$selection.find('.select2-selection__rendered');
+
+    Utils.appendMany($rendered, $selections);
   };
 
   return MultipleSelection;

src/js/select2/utils.js

@@ -241,5 +241,22 @@ define([
     });
   };
 
+  // Append an array of jQuery nodes to a given element.
+  Utils.appendMany = function ($element, $nodes) {
+    // jQuery 1.7.x does not support $.fn.append() with an array
+    // Fall back to a jQuery object collection using $.fn.add()
+    if ($.fn.jquery.substr(0, 3) === '1.7') {
+      var $jqNodes = $();
+
+      $.map($nodes, function (node) {
+        $jqNodes = $jqNodes.add(node);
+      });
+
+      $nodes = $jqNodes;
+    }
+
+    $element.append($nodes);
+  };
+
   return Utils;
 });