Multi Select Transfer just jQuery

Practicing using jMar's code from http://blog.jeremymartin.name/2008/02/easy-multi-select-transfer-with-jquery.html

HTML

<div>
    <select multiple id="select1">
        <option id="1" value="1">Option 1</option>
        <option id="2" value="2">Option 2</option>
        <option id="3" value="3">Option 3</option>
        <option id="4" value="4">Option 4</option>
    </select>
</div>
<div>
   <a href="#" id="add">&gt;&gt;</a><br/><a href="#" id="remove">&lt;&lt;</a> 
</div>
  
<div>
    <select multiple id="select2"></select>
</div>

CSS

a {
    
    border: 1px solid #aaa;
    text-decoration: none;
    background-color: #fafafa;
    color: #123456;
    margin: 2px;
    clear:both;
}
div {
    float:left;
    text-align: center;
    margin: 10px;
}
select {
    width: 100px;
    height: 80px;
}

JavaScript

$().ready(function () {

    $('#add').click(function () {
        var original = $('#select1 option:selected');
        var copied = $('#select1 option:selected').clone();
        copied.appendTo('#select2');
        original.remove();
        var selectList = $('#select2 option');
        selectList.sort(function (a, b) {
            a = a.value;
            b = b.value;
            return a - b;
        });
        $('#select2').html(selectList);
    });

    $('#remove').click(function () {
        var original = $('#select2 option:selected');
        var copied = $('#select2 option:selected').clone();
        copied.appendTo('#select1');
        original.remove();
        var selectList = $('#select1 option');
        selectList.sort(function (a, b) {
            a = a.value;
            b = b.value;
            return a - b;
        });
        $('#select1').html(selectList);
    });

});