Comment in JS code doesn't comment the server command. It is correct, but can be visually confusing. I had the following line in markup ASCX file.
// var trs = document.getElementById('<%=pnlOutsideSearch.ClientID %>').getElementsByTagName('TR');
Visual Studio showed it as green comment.
However when server control pnlOutsideSearch was renamed, the errors were generated, and it took me some time to realize, what wrong with the line, tha it was look like just comment.