select_all_facebook_friends_1.js

var friends = document.getElementById("friends").getElementsByTagName("a")
var clickEvent = document.createEvent("MouseEvents");
clickEvent.initMouseEvent("click", true, true, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
for(var i = 0; i < friends.length; i++) {friends[i].dispatchEvent(clickEvent);}

select_all_facebook_friends_2.js

javascript:f=document.getElementById("friends").getElementsByTagName("li");for(var i in f){if(typeof(f[i]) === "object"){fs.click(f[i])}}