title: how to check null in javaScript function?
body: <p>I want to check null and empty id in JavaScript function,but if syntax isn't work ?</p>
  
  <pre><code>var id = "&lt;%=Request["Id"]%&gt;";
   if (id !== "")
   if (id !== null)
  {var id = "&lt;%=new Guid(Request["ID"].ToString())%&gt;";
   window.location = "/Controller/Action.aspx?Id=" + id; }
  </code></pre>