jQuery UI select autocomplete

by Juan Muñoz

HTML

<link rel="stylesheet" href="//code.jquery.com/ui/1.12.1/themes/base/jquery-ui.css">
<button id="toggle">MOSTRAR|OCULTAR</button>
<div class="ui-widget">
	<label>Mostrar SELECT REAL </label>
	<select title="Empresa" id="empresa"  style="display:none;">
    <option value="#" selected="" disabled=""> Empresa </option>
    <option value="76160442-2"> ABOGADóS DEL MAULE</option>
    <option value="76157090-0"> AGRICOLA EL ALMENDRO LTDA.</option>
    <option value="76389930-6"> AGRÍCOLA EL ESFUERZO LTDA.</option>
    <option value="77741460-7"> AGRICOLA EL PERAL LTDA.</option>
    <option value="76434389-1"> AGRICOLA LAS ROCAS LTDA.</option>
    <option value="78833810-4"> AGRÍCOLA LONCOMILLA LTDA.</option>
    <option value="76186230-8"> AGRÍCOLA LOS ROBLES LTDA.</option>
    <option value="76763464-1"> AGRICOLA PERQUILAUQUEN SpA</option>
    <option value="9663898-K"> AGRÍCOLA PORTO FINO S.A.</option>
    <option value="89885100-1"> AGRÍCOLA Y COMERCIAL HUARACULÉN LTDA.</option>
    <option value="76043323-3"> AGRÍCOLA Y FORESTAL MIRA RIO LTDA.</option>
    <option value="5482402-5"> AGUSTÍN DEL CARMEN FUENTES ZAMORANO</option>
    <option value="76822641-5"> AK SpA</option>
    <option value="76301741-9"> ALEJANDRA BIANCHI ATHANACIU CUTIVO DE PLANTAS E.I.R.L.</option>
    <option value="12521053-8"> ALFONSO JOSÉ BARRIENTOS POZO</option>
    <option value="76340432-3"> ALMA COMUNICACIONES SOCIEDAD DE RESPONSABILIDAD LIMITADA</option>
    <option value="5796871-0"> ANATOLIO SEGUNDO ALBORNOZ VARGAS</option>
    <option value="76127917-3"> ASESORIAS E INVERSIONES EL TRAUCO LIMITADA</option>
    <option value="76752972-4"> ASESORIAS E INVERSIONES SAN CLEMENTE SpA</option>
    <option value="76068454-6"> ASESORIAS E INVERSIONES TORO ROSSO SpA</option>
    <option value="76404580-7"> ASESORIAS FORESTALES S.A.</option>
    <option value="76053424-2"> AUDITORES Y ABOGADOS ASOCIADOS LTDA.</option>
    <option value="76437236-0"> AUTOMOTRIZ Y NAUTICA SPA</option>
    <option...

CSS

.ui-autocomplete{
  background-color:gray;
  color:white;
}
.ui-autocomplete li{
  cursor:pointer;
}
.custom-combobox {
		position: relative;
		display: inline-block;
	}
	.custom-combobox-toggle {
		position: absolute;
		top: 0;
		bottom: 0;
		margin-left: -1px;
		padding: 0;
	}
	.custom-combobox-input {
		margin: 0;
		padding: 5px 10px;
	}

JavaScript

$(document).ready(function (){

		$.widget( "custom.combobox", {
			_create: function() {
				this.wrapper = $( "<span>" )
					.addClass( "custom-combobox" )
					.insertAfter( this.element );

				this.element.hide();
				this._createAutocomplete();
				this._createShowAllButton();
			},

			_createAutocomplete: function() {
				var selected = this.element.children( ":selected" ),
					value = selected.val() ? selected.text() : "";

				this.input = $( "<input>" )
					.appendTo( this.wrapper )
					.val( value )
					.attr( "title", "" )
					.addClass( "custom-combobox-input ui-widget ui-widget-content ui-state-default ui-corner-left" )
					.autocomplete({
						delay: 0,
						minLength: 0,
						source: $.proxy( this, "_source" )
					})
					.tooltip({
						classes: {
							"ui-tooltip": "ui-state-highlight"
						}
					});

				this._on( this.input, {
					autocompleteselect: function( event, ui ) {
						ui.item.option.selected = true;
						this._trigger( "select", event, {
							item: ui.item.option
						});
					},

					autocompletechange: "_removeIfInvalid"
				});
			},

			_createShowAllButton: function() {
				var input = this.input,
					wasOpen = false;

				$( "<a>" )
					.attr( "tabIndex", -1 )
					.attr( "title", "Show All Items" )
					.tooltip()
					.appendTo( this.wrapper )
					.button({
						icons: {
							primary: "ui-icon-triangle-1-s"
						},
						text: false
					})
					.removeClass( "ui-corner-all" )
					.addClass( "custom-combobox-toggle ui-corner-right" )
					.on( "mousedown", function() {
						wasOpen = input.autocomplete( "widget" ).is( ":visible" );
					})
					.on( "click", function() {
						input.trigger( "focus" );

						// Close if already visible
						if ( wasOpen ) {
							return;
						}

						// Pass empty string as value to search for, displaying all results
						input.autocomplete( "search", "" );
					});
			},

			_source: function( request, response ) {
				var matcher = new RegExp(...