$(this) always works on iteration

You cannot access  an element with $(this)  at event binding like this:

<select onclick="fun()">
....


fun()
{
 $(this).each(function ( )
{

.....

........

Reason : It works in iteration to refer to the element
                    $("select#"+id+" option:selected").each(function ( )
                   {
                          if($(this).val() =="Defined" )
                           {
   
                                    str=str+$(this).val();

                                   .............................

or you can also use that element at finction calling like this.....

<select id="xyz" onclick="fun(this.id)">