To invite all your friends to an event on Facebook without having to click every single friend one by one, follow this simple procedure:
1. Click Invite Friends on the Event Page.
2. Check all your friends you want to invite are listed in the box. (you may have to wait a second before they all appear so you can select them all. Friends that have not loaded onto the page yet will not get invited. If they don't all appear you can still go ahead but you may have to repeat this procedure.)
3. Right-click somewher on the page and choose the "Inspect Element" option from the drop-down list (available in most browsers.)
5. Copy and paste the following into your Console and press enter:
All your friends will now be selected. Note that if you scroll down now and load more friends and run this code again, it will uncheck the previous friends and select only the newly loaded ones.
6. Click the "Send" button. And you're done.
7. If you have a lot of friends you may have to repeat the procedure.