Facebook – How to Select All Friends

Currently there is no nice way of doing this. Fortunately, simply loading all of your friends and scanning down this list looking for "Add to List" is a fairly quick process. (Unless you have hundreds/thousands of friends...)

The code you mentioned does not work as Facebook UI has changed and it will continue to change. Nevertheless,

javascript:var x=document.getElementsByTagName("input");for(var i=0;i<x.length;i++) {if (x[i].type == 'checkbox') {x[i].click();}}; alert('Done, all your friends have been selected');

_{Source: http://olivo.net/2011/04/how-to-invite-all-your-facebook-friends-to-an-event-at-once-code-has-changed/}

Should do the trick. It works on the currently selected list. The above should not break in any future builds though as the only input elements on the page are your Facebook friends.