JSFiddle - React, Tailwind, and code Playground

HTML

<div id="targetDiv">
  <input id="StartStation" autocomplete="off" class="valid" type="text">
  <input id="SelectedStationStart" name="SelectedStationStart" type="hidden">
  <ul id="targetUI">
  <li id="359" onclick="javascript:setAutoComplete(359, 'Achim','StartStation','SelectedStationStart')">Achim</li>
  <li id="419" class=".selected" onclick="javascript:setAutoComplete(419, 'Achmer','StartStation','SelectedStationStart')">Achmer</li>
  <li id="1541" onclick="javascript:setAutoComplete(1541, 'Achmer (Bus)','StartStation','SelectedStationStart')">Achmer (Bus)</li>
  <li id="135" onclick="javascript:setAutoComplete(135, 'Bad Sachsa','StartStation','SelectedStationStart')">Bad Sachsa</li>
  <li id="283" onclick="javascript:setAutoComplete(283, 'Büsenbachtal','StartStation','SelectedStationStart')">Büsenbachtal</li>
  <li id="630" onclick="javascript:setAutoComplete(630, 'Flachsberg (Linie 641), Schwanewede','StartStation','SelectedStationStart')">Flachsberg (Linie 641), Schwanewede</li>
  <li id="528" onclick="javascript:setAutoComplete(528, 'Gertenbach','StartStation','SelectedStationStart')">Gertenbach</li>
  <li id="1121" onclick="javascript:setAutoComplete(1121, 'Golmbach','StartStation','SelectedStationStart')">Golmbach</li>
  <li id="973" onclick="javascript:setAutoComplete(973, 'Hachmühlen','StartStation','SelectedStationStart')">Hachmühlen</li>
  <li id="635" onclick="javascript:setAutoComplete(635, 'Meyenburg Wachendorf, Schwanewede','StartStation','SelectedStationStart')">Meyenburg Wachendorf, Schwanewede</li>
  </ul>
  </div>

CSS

#targetUI li {
                display: block;
                padding: 5px;
                background-color:#afefef;
                border: 1px solid #eeeeee;
                margin: 0px 0px;
                text-align:center;
}
#targetUI li.selected{
    background-color: #bbbbbb;
    color: #000000;
}
#targetUI li::selection {
    background-color: #00ff90;
    color: #000000;
}
#targetUI li:hover {
    background-color: #bbbbbb;
    color: #000000;
}
#targetUI{
        width:15em;
	background-color:#bbbbbb;
}
#targetUI ul{
    position:relative;
	right:1em;
	bottom:1em;
	background-color:#F0F4D6;
	border:1px solid #000000;
	padding: 0px;
	list-style: none;
}

JavaScript

var stationAction = "/AboTicketSystem/SelectStation";
            $(function () {
            
                $("#StartStation").on("keyup", function (e) {
                    //get value from input textbox
                    //scroll through list with keydown
                    if (e.keyCode == 40 || e.keyCode==38) { // down, up
                        var selected = $(".selected");
                        $("#targetUI li").removeClass("selected");                        
                        // if there is no element before the selected one, we select the last one
                        if (selected.prev().length == 0) {
                            selected.siblings().last().addClass("selected");
                        } else { // otherwise we just select the next one
                            selected.prev().addClass("selected");
                        }
                    }
                    else if(e.keyCode==13)
                    {
                        //set item to textbox
                        var selected = $(".selected");
                        selected.trigger("click");

                    }
                    else
                    {
                        var query = $(this).val();
                        //fetch values for searchterm
                        getItems(query, 'StartStation', 'SelectedStationStart', stationAction);
                    }
                });

                //call for Autocomplete Search 
                function getItems(query, parent, idField, computedurl) {
                    //handle search from inputfield

                    var postData = {
                        searchvalue: query
                    };
                    addAntiForgeryToken(postData);

                    request = $.ajax({
                        cache: false,
                        type: 'POST',
                        url: computedurl, 
                        data: postData,
                        dataType:...