I can’t get the src of image it is always undefined

I have a modal and I want to choose an image from this modal and when I click “ekle” button I want it to be shown in another div. I’m trying to do this with innerHTML but image src is undefined.
Is there a better way then innerHTML?
If there is no better way how can I fix this undefined problem.

function testFunction() {
    var imagesrc = document.getElementsByClassName("selected").src;
    document.getElementById("deneme").innerHTML = '<img src="' + imagesrc + '" >';
}
<div class="modal fade" id="hazirresim" tabindex="-1" role="dialog" aria-labelledby="exampleModalCenterTitle" aria-hidden="true">
    <div class="modal-dialog modal-dialog-centered modal-lg" role="document">
        <div class="modal-content">
            <div class="modal-header">
                <h5 class="modal-title" id="exampleModalLongTitle">Kategori Hazır Resimleri</h5>
                <button type="button" class="close" data-dismiss="modal" aria-label="Close">
                    <span aria-hidden="true">&times;</span>
                </button>
            </div>
            <div class="modal-body">
                <input type="image" src="images/lol-1.jpg" class="selectable" height="250" width="250" style="padding-right: 3px;padding-bottom: 3px;">
                <input type="image" src="images/lol-1.jpg" class="selectable" height="250" width="250" style="padding-right: 3px;padding-bottom: 3px;">
                <input type="image" src="images/lol-1.jpg" class="selectable" height="250" width="250" style="padding-right: 3px;padding-bottom: 3px;">
                <input type="image" src="images/lol-1.jpg" class="selectable" height="250" width="250" style="padding-right: 3px;padding-bottom: 3px;">
                <input type="image" src="images/lol-1.jpg" class="selectable" height="250" width="250" style="padding-right: 3px;padding-bottom: 3px;">
                <input type="image" src="images/lol-1.jpg" class="selectable" height="250" width="250" style="padding-right: 3px;padding-bottom: 3px;">
            </div>
            <div class="modal-footer">
                <button onclick="testFunction();" type="button" class="btn btn-info btn-lg btn-block">EKLE</button>
            </div>
        </div>
    </div>
</div>