How to pass a parameter to setTimeout callback?

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C#

ASP.NET

Javascript

I have a function in javascript

function onGet(buttonid) {
//             debugger;
             var bt = document.getElementById(buttonid);
             to = setTimeout('performSearch();', 300);
         }

and another function with in the script is performSearch() and i want to pass "bt" in to performSearch(). How can i do this?

function performSearch(bt) {
             debugger;
             if (prm.get_isInAsyncPostBack) {
                 prm.abortPostBack();
             }
             $get("<%=lblStatus.ClientID %>").innerHTML = "Loading...";