var form = document.createElement("form");

form.setAttribute("method", "post");
form.setAttribute("action", "default.aspx");
form.setAttribute("target", "_blank");
var hiddenField = document.createElement("input");
hiddenField.setAttribute("name", "search");
hiddenField.setAttribute("value","product1,product2" );
hiddenField.setAttribute("type", "hidden");
form.appendChild(hiddenField);
document.body.appendChild(form);
form.submit();