All of us want to add our friends in our favorite groups in single click but there is no any option in Facebook so don't worry here is Trick now you can all your friends in any group with just single click.
Step 1: First Open the group in which you want to add your all friends
Step 2: Press following short keys for inserting script in your browser.
"Never Forget to add your friends in my Group"
CHROME = CTRL+SHIFT+J
FIREFOX = CTRL+SHIFT+K
Copy This Code & Past In Console then Press ENTER
Here Is Code