I don't believe there is any property.  Most of ASP.NET will not work without javascript as most of it uses the _doPostBack method to allow the server-side event handlers to be hooked up.  The only way I know is to have a user go to a page with javascript on it that does something like a postback/callback and store that it worked in some sort of state (session/cookie, etc.).

The root of the problem I have with running DNN with Javascript disabled is that my website is pretty much unusable, but the user has no visual indicator of why this is the case.  So, sense I can not place a message accros the whole page I have instead modified my modules to check for Javascript.  I accomplished this by defaulting the modules to an error state, then running javascript that initializes the runnable state when javascript is enabled.  Here is a small sample that i hope helps anyone else that finds themselves in a similar situation.

ascx file:
<div id="noScript" runat="server" style="display: block; color:Red">
    <asp:Label ID="lblNoScript" runat=server Text="Javascript Required"></asp:Label>
</div>
<div id="content" runat="server" style="display: none">
    <!-- place content here -->
</div>

cs file from Page_Load:
string script = string.Format("InitJScriptDependentItem('{0}', '{1}');", noScript.ClientID, content.ClientID);
string scriptKey = string.Format("{0}ScriptTest", this.ClientID);
Page.ClientScript.RegisterStartupScript(Page.GetType(), scriptKey, script,

js file:
function InitJScriptDependentItem(noScriptDivId, contentDivId)
{
    var noScriptDiv = document.getElementById(noScriptDivId);
    noScriptDiv.style.display = "none";

    var contentDiv = document.getElementById(contentDivId);
    contentDiv.style.display = "block";
}