JQuery keydown event changes removed when letting go of key

I am trying to create an auto-suggest box. When a user starts typing in the #tagSelection input field, JQuery fetches suggestions from the database through Ajax and display these in the #suggestBox div that is displayed right under the #tagSelection field.

Now I want to enable the user to use the arrow down key to select one of the suggestions. I have started building this by handling the keydown() event and assigning a class to the first entry during this event. The problem I am facing is that the class is removed again when I let go of the arrow down key. I need it to stay assigned when I let go of the key. Is that possible?

The HTML

<div class="form-entry">
    <input id="tagSelection" name="tags" type="text" value="" size="40">

    <div id="suggestBox" style="">
        <a href="#" id="1">design</a>
        <a href="#" id="3">debit card</a>
        <a href="#" id="4">deer</a>
    &nbsp;
    <a href="#" id="addTag">Add word</a>

    <div id="selectedTags"></div>

</div>

The JQuery

(function() {
    $('#tagSelection').keydown(downArrowKeyHandler);
})();

function downArrowKeyHandler(event) {
    if (event.keyCode == 40) {
        if ($('#suggestBox').length > 0) {
            if ($('[tagSelected = 1]').length == 0) {
                // the tagSelected class gives the entry a colored background
                $('#suggestBox').children().filter(':first').addClass('tagSelected');
            }
        }
    }
}

Solution

I found the exact same problem here:

How to make a permanent change to an element after using jQuery's .keydown()?

It seems I indeed had some other JQuery code that was interfering with my event handler. Whenever someone releases a key when in the #tagSelection field a JQuery method fires that retrieves the suggestions from the db. The already present keyup() event was interfering with my new keydown() event.

(function() {
    $('#tagSelection').keyup(tagboxTypingHandler)
})();


function tagboxTypingHandler(event) {
    if (event.keyCode != 40) {
        var substring = $('#tagSelection').val();
        if (substring.length > 1) {
            $.get("http://localhost:8080/tag/search/" + substring, returnedTagsHandler);
        }
    }
}

I just added the event.keyCode != 40 condition and now the class remains on the suggestion and it works :-)