https://www.creatio.com/libraries/select2.position.js?v=1.4.8

1(function($) {
2
3  var Defaults = $.fn.select2.amd.require('select2/defaults');
4
5  $.extend(Defaults.defaults, {
6    dropdownPosition: 'auto'
7  });
8
9  var AttachBody = $.fn.select2.amd.require('select2/dropdown/attachBody');
10
11  var _positionDropdown = AttachBody.prototype._positionDropdown;
12
13  AttachBody.prototype._positionDropdown = function() {
14
15    var $window = $(window);
16
17    var isCurrentlyAbove = this.$dropdown.hasClass('select2-dropdown--above');
18    var isCurrentlyBelow = this.$dropdown.hasClass('select2-dropdown--below');
19
20    var newDirection = null;
21
22    var offset = this.$container.offset();
23
24    offset.bottom = offset.top + this.$container.outerHeight(false);
25
26    var container = {
27      height: this.$container.outerHeight(false)
28    };
29
30    container.top = offset.top;
31    container.bottom = offset.top + container.height;
32
33    var dropdown = {
34      height: this.$dropdown.outerHeight(false)
35    };
36
37    var viewport = {
38      top: $window.scrollTop(),
39      bottom: $window.scrollTop() + $window.height()
40    };
41
42    var enoughRoomAbove = viewport.top < (offset.top - dropdown.height);
43    var enoughRoomBelow = viewport.bottom > (offset.bottom + dropdown.height);
44
45    var css = {
46      left: offset.left,
47      top: container.bottom
48    };
49
50    // Determine what the parent element is to use for calciulating the offset
51    var $offsetParent = this.$dropdownParent;
52
53    // For statically positoned elements, we need to get the element
54    // that is determining the offset
55    if ($offsetParent.css('position') === 'static') {
56      $offsetParent = $offsetParent.offsetParent();
57    }
58
59    var parentOffset = $offsetParent.offset();
60
61    css.top -= parentOffset.top
62    css.left -= parentOffset.left;
63
64    var dropdownPositionOption = this.options.get('dropdownPosition');
65
66    if (dropdownPositionOption === 'above' || dropdownPositionOption === 'below') {
67      newDirection = dropdownPositionOption;
68    } else {
69
70      if (!isCurrentlyAbove && !isCurrentlyBelow) {
71        newDirection = 'below';
72      }
73
74      if (!enoughRoomBelow && enoughRoomAbove && !isCurrentlyAbove) {
75        newDirection = 'above';
76      } else if (!enoughRoomAbove && enoughRoomBelow && isCurrentlyAbove) {
77        newDirection = 'below';
78      }
79
80    }
81
82    if (newDirection == 'above' ||
83      (isCurrentlyAbove && newDirection !== 'below')) {
84      css.top = container.top - parentOffset.top - dropdown.height;
85    }
86
87    if (newDirection != null) {
88      this.$dropdown
89        .removeClass('select2-dropdown--below select2-dropdown--above')
90        .addClass('select2-dropdown--' + newDirection);
91      this.$container
92        .removeClass('select2-container--below select2-container--above')
93        .addClass('select2-container--' + newDirection);
94    }
95
96    this.$dropdownContainer.css(css);
97
98  };
99
100})(jQuery);