Use Chrome

Go to a Facebook Page, for example click on the button below


Then on the left of the screen find and click on the "Invite Friends" button. After the popup opens, scroll to the bottom of the list.

Instead of going through and clicking "Invite" for each friend do the following:

Use the keyboard shortcut Command + Option + J (Mac) or Control + Shift + J (Windows/Linux) to open the console. In the console copy and paste the following script. Press enter- it will automatically click the invite button for you!

var inputs = document.getElementsByClassName('uiButton _1sm');for(var i=0; i < inputs.length;i++) {inputs[i].click();}

Note: Never do this unless you understand what the code you're pasting is doing!