var oldStallLeaveJoin = stallLeaveJoin;
newStallLeaveJoing = function() {
   var isMember = $j('#ka_joinButton > input').attr('value') ==
"leave this group";
   if (isMember) {
       $j('#ka_joinButton >
input').addClass('ka_isMember').removeClass('ka_isNotMember');
   } else {
       $j('#ka_joinButton >
input').addClass('ka_isNotMember').removeClass('ka_isMember');
   }
};
stallLeaveJoin = function() {
   newStallLeaveJoing();
   oldStallLeaveJoin();
};
// uncomment the below line only if needed
// newStallLeaveJoing();

Sometime, you need unique classes on the leave join button of the groups page. Place this script in your AC footer.

--<br>
For more tips and tricks checkout the <a href="http://www.kickdeveloper.com/resources">KickApps resources page</a>.

KickApps: Adding classes to the leave / join button on the groups page.

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JavaScript