How to modify dimensions of a div during run time based on dimension of its control

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ASP.NET

Javascript

I have a div and a gridview in my page as shown below:

<div id="gdDiv" style="overflow:scroll; height:500px; width:1270px; background-color:Black;" onload="MakeEqualDimension()">
            <asp:GridView ID="gdView" runat="server" Width="1200px" Height="350px"  
                RowStyle-HorizontalAlign="Center" RowStyle-VerticalAlign="Middle" 
                HeaderStyle-HorizontalAlign="Center" HeaderStyle-BackColor="Maroon" 
                HeaderStyle-ForeColor="White" HeaderStyle-Height="5px" 
                RowStyle-BackColor="Black" RowStyle-ForeColor="White"  GridLines="Both" 
                ShowFooter="true" RowStyle-Wrap="false" onrowcreated="gdView_RowCreated" 
                onrowdatabound="gdView_RowDataBound" HeaderStyle-Font-Size="10px" RowStyle-Font-Size="10px" HeaderStyle-Font-Bold="true" FooterStyle-Font-Bold="true" FooterStyle-Font-Size="10px">
            </asp:GridView>
        </div>

The gridview is populated dynamically and so its height and width varies depending upon the number of data. I want the div also to change its height and width based on the height & width of the gridview after it is populated.

What I have tried:

Hence I have tried the following javascript in the client side.

<script type="text/javascript">
    function MakeEqualDimension() 
    {
        if ((document.getElementById('gdDiv').offsetHeight) >
        (document.getElementById('gdView').getAttribute("height"))) 
        {
            document.getElementById('gdDiv').style.height =
          (document.getElementById('gdView').getAttribute("height")) + "px";
        }
        if ((document.getElementById('gdDiv').style.width) >
        (document.getElementById('gdView').getAttribute("width"))) 
        {
            document.getElementById('gdDiv').width =
          (document.getElementById('gdView').getAttribute("width")) + "px";
        }
    }
</script>

But its not working. Please help me. Thanks.