Set the iframe src from javascript in asp.net

how to set the iframe src from javascript in asp.net

var iframesrc = "../ChildPages/Search.aspx?sDate='" + sDate + "'&&eDate='" + eDate + "'";
document.getElementById("iframesearch").setAttribute("src", iframesrc);  // set the attribute for control


<iframe id="iframesearch" src=""></iframe>