Code:
<div id='external-events'>
<div class="Item">
<span class="ItemDrag" id="Max, Moritz" data-id="1">Max, Moritz</span>
</div>
<div class="Item">
<span class="ItemDrag" id="Hänsel, Gretel" data-id="2">Hänsel, Gretel</span>
</div>
</div>
<script>
var s = document.getElementById('Max, Moritz');
alert(s);
var a = s.attr("data-id");
alert(a);
</script>