starting from mihai-labo's answer, why not skip declaring the requrl variable altogether and put the url generating code directly in front of "url:", like:
$.ajax({
type: "POST",
url: '@Url.Action("Action", "Controller", null, Request.Url.Scheme, null)',
data: "{queryString:'" + searchVal + "'}",
contentType: "application/json; charset=utf-8",
dataType: "html",
success: function (data) {
alert("here" + data.d.toString());
}
});