dom parent and child relation

Question

<div class="col-md-12">

<span class="unit-cost">Rs.<asp:Label ID="lblunitcost" CssClass="unitcost" runat="server"></asp:Label></span>

<span class="offer-price"><asp:Label ID="lblDelarcost" CssClass="delarcost" runat="server"></asp:Label></span>

</div>

<div class="col-md-12" align="right">

<asp:DropDownList ID="ddlmodel" runat="server" CssClass="qty-box" OnSelectedIndexChanged="ddlmodel_SelectedIndexChanged" AutoPostBack="false" onchange="onModelChange(this)">

</asp:DropDownList>

</span>

 

<script>

var showingcost=$(element).parent('span').parent('div').prev('div').childNodes[0];

showingcost.text(unit);

var showdelarcost=$(element).parent('span').parent('div').prev('div').secondChild('span');

showdelarcost.text(dealer);

 

</script> 

 its not working?