<asp:DropDownList ID="ddlPUom" runat="server" CssClass="form-control input-sm"></asp:DropDownList>



<asp:Label ID="lblpuom" ccclass="col-xs-2 control-label" runat="server" Text=""></asp:Label>


<script type="text/javascript">
    $('#ddlPUom').change(function () {
        alert("did this fire?");
        var lbltext = doc.getElementById("ddlPUom");
        var lblPUOM = doc.getElementById("lblpuom");
        lblPUOM.lbltext = lbltext.innerhtml;
    });
</script>

<script type="text/javascript">
    $('#ddlPUom').change(function () {
        alert("did this fire?");
        var lbltext = doc.getElementById("<%=ddlPUom.ClientID%>");
        var lblPUOM = doc.getElementById("<%=lblpuom.ClientID%>");
        lblPUOM.lbltext = lbltext.innerhtml;
    });
</script>

$(document).ready(function(){
$('#<%=ddlPUom.ClientID%>').change(function () {
            alert("did this fire?");
    }
});