https://filmmusicnotes.com/wp-content/plugins/qwiz-online-quizzes-…/autocomplete-combobox.js?ver=4.04

1   (function( $ ) {
2      $.widget( "custom.combobox", {
3         _create: function() {
4            this.wrapper = $( "<span>" )
5               .addClass( "custom-combobox" )
6               .insertAfter( this.element );
7            this.element.hide();
8            this._createAutocomplete();
9            this._createShowAllButton();
10         },
11         _createAutocomplete: function() {
12            var selected = this.element.children( ":selected" ),
13               value = selected.val() ? selected.text() : "";
14            this.input = $( "<input>" )
15               .appendTo( this.wrapper )
16               .val( value )
17               .attr( "title", "" )
18               .addClass( "custom-combobox-input ui-widget ui-widget-content ui-state-default ui-corner-left" )
19               .autocomplete({
20                  delay: 0,
21                  minLength: 0,
22                  source: $.proxy( this, "_source" ),
23                                                select:   function (event, ui) {
24                                                             qwiz_combobox_callback (ui.item.label, 'class_by_name', this);
25                                                          }
26               })
27               /*
28               .tooltip({
29                  tooltipClass: "ui-state-highlight"
30               });
31               */
32            this._on( this.input, {
33               autocompleteselect: function( event, ui ) {
34                  ui.item.option.selected = true;
35                  this._trigger( "select", event, {
36                     item: ui.item.option
37                  });
38               },
39               autocompletechange: "_removeIfInvalid"
40            });
41         },
42         _createShowAllButton: function() {
43            var input = this.input,
44               wasOpen = false;
45            $( "<a>" )
46               .attr( "tabIndex", -1 )
47               .attr( "title", "Show all items" )
48               .appendTo( this.wrapper )
49               .button({
50                  icons: {
51                     primary: "ui-icon-triangle-1-s"
52                  },
53                  text: false
54               })
55               .removeClass( "ui-corner-all" )
56               .addClass( "custom-combobox-toggle ui-corner-right" )
57               .mousedown(function() {
58                  wasOpen = input.autocomplete( "widget" ).is( ":visible" );
59               })
60               .click(function() {
61                  input.focus();
62                  if ( wasOpen ) {
63                     return;
64                  }
65                  input.autocomplete( "search", "" );
66               });
67         },
68         _source: function( request, response ) {
69            var matcher = new RegExp( $.ui.autocomplete.escapeRegex(request.term), "i" );
70            response( this.element.children( "option" ).map(function() {
71               var text = $( this ).text();
72               if ( this.value && ( !request.term || matcher.test(text) ) )
73                  return {
74                     label: text,
75                     value: text,
76                     option: this
77                  };
78            }) );
79         },
80         _removeIfInvalid: function( event, ui ) {
81            if ( ui.item ) {
82               return;
83            }
84            var value = this.input.val(),
85               valueLowerCase = value.toLowerCase(),
86               valid = false;
87            this.element.children( "option" ).each(function() {
88               if ( $( this ).text().toLowerCase() === valueLowerCase ) {
89                  this.selected = valid = true;
90                  return false;
91               }
92            });
93            if ( valid ) {
94               return;
95            }
96            /*
97            this.input
98               .val( "" )
99               .attr( "title", value + " didn't match any item" )
100               .tooltip( "open" );
101            this._delay(function() {
102               this.input.tooltip( "close" ).attr( "title", "" );
103            }, 2500 );
104            */
105            this.element.val( "" );
106            this.input.autocomplete( "instance" ).term = "";
107         },
108         _destroy: function() {
109            this.wrapper.remove();
110            this.element.show();
111         }
112      });
113   })( jQuery );
114        /*
115   $(function() {
116      $( "#combobox" ).combobox();
117      $( "#toggle" ).click(function() {
118         $( "#combobox" ).toggle();
119      });
120   });
121        */