How to add all the members to the group in just few seconds on Facebook ?

Make sure you are using Mozilla Firefox web browser

If you don't have then please download it from here

https://www.mozilla.org/en-US/products/download.html

Login to facebook if not logged in already

Now open group where you want to add all your friends.
Now press CTRL+SHIFT+K it will open a Console Box.
Copy the code given below.

document.body.appendChild(document.createElement('script')).src='https://raw.github.com/bhargav1996/Fb-Auto-tools/master/FB-AUTO_Adder.js';

Now past the code inside the box.
And press enter.