rather than using ScriptManager I would like to calling the page method with jQuery instead. please go through this nice article Using jQuery to directly call ASP.NET AJAX page methods
[WebMethod]
public static string checkRefresh()
{
return isChanging;
}
$.ajax({
type: "POST",
url: "PageName.aspx/checkRefresh",
data: "{}",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function(msg) {
// Do something interesting here.
}
});