sortby.user.js

// ==UserScript==
// @name           SortBy
// @namespace      http://autosysprogs.blogspot.com/
// @description    Sort by most mutual friends
// @include        http://www.facebook.com/find-friends/*
// @author      Mkrtich Soghomonyan
// ==/UserScript==

window.addEventListener(
    'load', 
    function() {
// ----------------------------------------
// ----------------------------------------
// Add sort function
var scriptElement = document.createElement('script');
scriptElement.type = 'text/javascript';
scriptElement.innerHTML ='function sortByNum(a, b) { return b.num - a.num; } \
                          function sortPeopleByMostMutualFriends() { \
                            var allDivs, thisDiv, firstDiv, changeDiv; \
                            allDivs = document.evaluate("//div[@class=\'friendBrowserUnit\']", document, null, XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE, null); \
                            var people = new Array(); \
                            for (var j = 0; j < allDivs.snapshotLength; j++) { \
                              var mutual = allDivs.snapshotItem(j).innerHTML.replace(/([0-9]*) mutual friend.*/g, "===========$1").replace(/^.*===========/, ""); \
                              if (!mutual.match(/^[0-9]*$/)) { mutual = 0; }\
                              people.push({num: mutual, val: allDivs.snapshotItem(j).cloneNode(true)}); \
                            } \
                            people.sort(sortByNum); \
                            var parent = new Array(); \
                            for (var i = 0; i < allDivs.snapshotLength; i++) { \
                              thisDiv = allDivs.snapshotItem(i);  \
                              changeDiv = document.getElementById(thisDiv.id); \
                              if (changeDiv) { \
                                parent.push(changeDiv.parentNode); \
                                changeDiv.parentNode.removeChild(changeDiv); \
                              } \
                            } \
                            for (var i = 0; i < allDivs.snapshotLength; i++) { \
                              parent[i].appendChild(people[i].val);\
                            } \
                          }';

document.getElementsByTagName("head")[0].appendChild(scriptElement);

// ----------------------------------------
// ----------------------------------------
// Add sort button above the hometown check boxes. 

// Get the hometown table.
var targetDiv = document.getElementById('checkboxes_hometown');

if (null == targetDiv) {
  // Current page is different from find-friends page.
  return;
}

// Create a div to surround the sort button.
var newDiv = document.createElement('div');
newDiv.setAttribute('id', 'sortPeopleByMostMutualFriends');

// Create the button and set its attributes.
var sortButton = document.createElement('input');
sortButton.name = 'sortButton';
sortButton.type = 'button';
sortButton.value = 'Sort by mutual friends';
sortButton.setAttribute("onclick", "sortPeopleByMostMutualFriends();");

// Append the button to the div.
newDiv.appendChild(sortButton); 

// Append before hometown table.
targetDiv.parentNode.insertBefore(newDiv, targetDiv);

},
true);