What is CavalryLogger and do I need it?

Question

I'm doing some optimisation on a site Ive recently taken over. I've found a script I don't recognise: http://static.ak.fbcdn.net/rsrc.php/zo/r/V95Lkt_uLNB.js

It could be a facebook thing, and there's some key logging going on (that Im not too keen on)

It is without a doubt the largest file being requested on a page load (87kb) so if I can do without it, it'll really speed up the page load.

Does anyone know:
A) What it is
B) What it's for
C) What it does
D) Can I do without it

Answer 1

Okay so I had a look over the beautified version of this minified code and have noted the following:

By itself these are a bunch of utility functions.

CavalryLogger doesn't do anything with this file by itself because it doesn't exist, nor is it defined.

The code in question regarding key binding:

function KeyEventController() {
  copy_properties(this, {
    handlers: {}
  });
  document.onkeyup = this.onkeyevent.bind(this, 'onkeyup');
  document.onkeydown = this.onkeyevent.bind(this, 'onkeydown');
  document.onkeypress = this.onkeyevent.bind(this, 'onkeypress');
}
copy_properties(KeyEventController, {
  instance: null,
  getInstance: function () {
    return KeyEventController.instance || (KeyEventController.instance = new KeyEventController());
  },
  defaultFilter: function (event, a) {
    event = $E(event);
    return KeyEventController.filterEventTypes(event, a) && KeyEventController.filterEventTargets(event, a) && KeyEventController.filterEventModifiers(event, a);
  },
  filterEventTypes: function (event, a) {
    if (a === 'onkeydown') return true;
    return false;
  },
  filterEventTargets: function (event, b) {
    var a = $E(event).getTarget();
    if (DOM.isNode(a, ['input', 'select', 'textarea', 'object', 'embed'])) if (a.type != 'checkbox' && a.type != 'radio' && a.type != 'submit') return false;
    return a.getAttribute('contentEditable') != 'true';
  },
  filterEventModifiers: function (event, a) {
    if (event.ctrlKey || event.altKey || event.metaKey || event.repeat) return false;
    return true;
  },
  registerKey: function (f, a, d, g) {
    if (d === undefined) d = KeyEventController.defaultFilter;
    var b = KeyEventController.getInstance();
    var c = b.mapKey(f);
    if (is_empty(b.handlers)) onleaveRegister(b.resetHandlers.bind(b));
    for (var e = 0; e < c.length; e++) {
      f = c[e];
      if (!b.handlers[f] || g) b.handlers[f] = [];
      b.handlers[f].push({
        callback: a,
        filter: d
      });
    }
  },
  keyCodeMap: {
    '[': [219],
    ']': [221],
    '`': [192],
    LEFT: [KEYS.LEFT, 63234],
    RIGHT: [KEYS.RIGHT, 63235],
    RETURN: [KEYS.RETURN],
    TAB: [KEYS.TAB],
    DOWN: [KEYS.DOWN, 63233],
    UP: [KEYS.UP, 63232],
    ESCAPE: [KEYS.ESC],
    BACKSPACE: [KEYS.BACKSPACE],
    DELETE: [KEYS.DELETE]
  }
});
copy_properties(KeyEventController.prototype, {
  mapKey: function (a) {
    if (typeof (a) == 'number') return [48 + a, 96 + a];
    if (KeyEventController.keyCodeMap[a.toUpperCase()]) return KeyEventController.keyCodeMap[a.toUpperCase()];
    var b = a.toUpperCase().charCodeAt(0);
    return [b];
  },
  onkeyevent: function (i, c) {
    c = $E(c);
    var d = null;
    var g = this.handlers[c.keyCode];
    var b, f, a;
    if (g) for (var h = 0; h < g.length; h++) {
      b = g[h].callback;
      f = g[h].filter;
      try {
        if (!f || f(c, i)) {
          var node = null;
          if (window.Parent && Parent.byTag && c.getTarget) node = Parent.byTag(c.getTarget(), 'a');
          user_action(node, 'key', c);
          a = b(c, i);
          if (a === false) return Event.kill(c);
        }
      } catch (e) {}
    }
    return true;
  },
  resetHandlers: function () {
    this.handlers = {};
  }
});

This code lets you bind keys to callbacks, and includes more human readable names for common keys. Take for example the usage here:

KeyEventController.registerKey('ESCAPE', Dialog._handleEscapeKey, a);

The ESCAPE key is registered to make Dialogs go away. handlers is also empty by default, so nothing is going to happen until you use registerKey or append to it manually. Note that this is the only instance of registerKey being called.

It also has a lot of AJAX utility functions. Can't really send anything to Facebook from your domain anyways because of same origin policy (unless you modified security permissions, but then that's your fault). Same thing with the cookies set.

There's also a history manger, but it uses an iFrame so it won't be able to read it from your domain anyways.

Finally the like button code I found is an iFrame, so it wouldn't need JS includes unless you were using javascript to create the iFrame or something.

With that in mind I don't see the need for you to include all this.

Answer 2

It looks like this is directly connected to having the "Like this" functionality on a page. The iframe you use to include the 'Like' button seems to come with a couple of 'bonus' scripts.

If you ask me, this is another good reason to NOT have Facebook integrated, it appears to be logging keypresses, and that is not cool.

Answer 3

A quick google search doesn't provide alot of answers - it's some sort of event tracking script for Facebook, and I saw a tweet and a couple of forum posts where people mentioned disabling it and gaining a speed boost - I think you can safely get rid of it, atleast it's worth giving it a try.