<div id="e_1">hey!</div>
<script>
var someId = 1;
var myId = "e_" + someId;
var myNativeDiv = document.getElementById(myId).innerHTML;
var myjQueryDiv = $("#" + myId).html();
alert(myNativeDiv + " - " + myjQueryDiv); // alerts "null - [Object object]"
</script>