Autocomplete Combobox

HTML

Your preferred programming language:
<div class="ui-widget">
    <select id="combobox">
        <option value="">Select one...</option>
        <option value="ActionScript">ActionScript</option>
        <option value="AppleScript">AppleScript</option>
        <option value="Asp">Asp</option>
        <option value="BASIC">BASIC</option>
        <option value="C">C</option>
        <option value="C++">C++</option>
        <option value="Clojure">Clojure</option>
        <option value="COBOL">COBOL</option>
        <option value="ColdFusion">ColdFusion</option>
        <option value="Erlang">Erlang</option>
        <option value="Fortran">Fortran</option>
        <option value="Groovy">Groovy</option>
        <option value="Haskell">Haskell</option>
        <option value="Java">Java</option>
        <option value="JavaScript">JavaScript</option>
        <option value="Lisp">Lisp</option>
        <option value="Perl">Perl</option>
        <option value="PHP">PHP</option>
        <option value="Python">Python</option>
        <option value="Ruby">Ruby</option>
        <option value="Scala">Scala</option>
        <option value="Scheme">Scheme</option>
    </select>
</div>
<!-- Post Info -->
<div style='position:fixed;bottom:0;left:0;    
            background:lightgray;width:100%;'>
    Related to this SO question: <a href='http://stackoverflow.com/q/16799781/1366033'>Fire DropDownList SelectedIndexChanged event</a><br/>
    Related to this SO question: <a href='http://stackoverflow.com/q/16617095/1366033'>Select Text on Focus of Input Element </a><br/>
    Further Reading: <a href='http://www.learningjquery.com/2010/06/a-jquery-ui-combobox-under-the-hood'>A jQuery UI Combobox: Under the hood</a>
    <br/>Find documentation: <a href='http://jqueryui.com/autocomplete/#combobox'>jQuery UI Autocomplete ComboBox Demo</a>
    <br/>Find documentation: <a href='http://api.jqueryui.com/autocomplete/'>jQuery UI Autocomplete ComboBox API</a>

    <div>

CSS

.custom-combobox {
    position: relative;
    display: inline-block;
}
.custom-combobox-toggle {
    position: absolute;
    top: 0;
    bottom: 0;
    margin-left: -1px;
    padding: 0;
    /* support: IE7 */
    *height: 1.7em;
    *top: 0.1em;
}
.custom-combobox-input {
    margin: 0;
    padding: 0.3em;
}
.ui-autocomplete {
    /* these sets the height and width */
    max-height: 250px;
    /* support: IE7 */
    *height: 250px;
    /* these make it scroll for anything outside 
    overflow: scroll;*/
    overflow-x:hidden;
    overflow-y:scroll;
}

JavaScript

$(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({
                    tooltipClass: "ui-state-highlight"
                }).on('mouseup', function() {
                    $(this).select();
                });

            this._on(this.input, {
                autocompleteselect: "_selectFromMenu",
                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")
                .mousedown(function () {
                wasOpen = input.autocomplete("widget").is(":visible");
            })

               ...