How can i prevent myself to being added in facebook groups?

[Hasnain]

This is what i found in Facebook Help Centre:
"Can I prevent people from adding me to a new group?
The functionality of approving a group membership is not available. Similar to being tagged in a photo, you can only be added to a group by one of your friends. When a friend adds you to a group, a story in the group (and in News Feed for Open or Closed groups) will indicate that your friend has added you to a group.

Please keep in mind:

*Only your friends can add you to groups.
*When a friend adds you to a group, you'll get a notification right away.
*You can leave a group anytime. To do so, just go to the group page and click "Leave Group" in the right-hand column. Once you leave a group, you can't be added by anyone else unless you explicitly request to be re-added."