To invite all of your friends to your Facebook group you have many options, Chrome plugins and scripts are plentiful. I will give you the the top methods of Facebook Group Invite All Friends for 2017.
Check it out here Facebook Group Add All Friends. The extension was designed and built here in house at fbadded.com
Second is the Facebook Group Invite All extension for chrome found here.. https://chrome.google.com/webstore/detail/group-invite-all/eeajicmampllnpkmfimkhefbndkfeloo?hl=en-US
This chrome extension can invite all of your friends to your facebook group in theory, though in practice it is actually only capable of adding from 250 to 700 before your account gets restricted from adding to groups and you have to wait for a time until you can use it again. so its not really adding all of your friends to your group if you have lots of friends.
Though if you have multiple Facebook accounts and you want to add all of the friends to your group then you could use this chrome extension to invite 500 per day to your group and continue the process until your group gets blocked from receiving new members.
Your group can be blocked from having new members added from as little as 1500 to sometimes 10000 members added, it will depend on how big the group is and how much adding you have previously done. It actually also depends on who made the group and how many groups they have previously created.
The second option to Facebook Group Invite All Friends is a little more gentle approach and can be more effective. The Ad Added Tool Kit or previously Facebook Social Media Toolkit can be found here https://chrome.google.com/webstore/detail/toolkit-for-facebook/fcachklhcihfinmagjnlomehfdhndhep?hl=en-US
There are many features with the tool kit but the group invite tool is more sophisticated than the other plugin because it allows yu to set a delay between the adding of 2 people. from 0 to xxx seconds. So it is actually possible to add more people to a group in one go by setting the delay higher and avoiding restrictions. you will ultimately hit the wall and be blocked but you will have added more members before you hit that wall. The down side is that you may have to wait a fair long time for the process to complete.
The 3rd way to invite all to your Facebook group is a very dangerous trick, it works well and it is the fastest but it carries a certain amount of risk.
For more info on adding to Facebook groups with codes and why not to do it, please check out this post.