Listening for Youtube Event in JavaScript or jQuery

The YouTube Frame API does support existing frames. To improve the usage, I have created some helper functions. Have a look at the code + comments below and the demo: http://jsfiddle.net/YzvXa/197

To bind functions to existent frames, you have to pass an ID reference to the frame. In your case, the frame is contained within a container with id="tab2". I have defined a custom function for an easier implementation:

function getFrameID(id){
    var elem = document.getElementById(id);
    if (elem) {
        if(/^iframe$/i.test(elem.tagName)) return id; //Frame, OK
        // else: Look for frame
        var elems = elem.getElementsByTagName("iframe");
        if (!elems.length) return null; //No iframe found, FAILURE
        for (var i=0; i<elems.length; i++) {
           if (/^https?:\/\/(?:www\.)?youtube(?:-nocookie)?\.com(\/|$)/i.test(elems[i].src)) break;
        }
        elem = elems[i]; //The only, or the best iFrame
        if (elem.id) return elem.id; //Existing ID, return it
        // else: Create a new ID
        do { //Keep postfixing `-frame` until the ID is unique
            id += "-frame";
        } while (document.getElementById(id));
        elem.id = id;
        return id;
    }
    // If no element, return null.
    return null;
}

// Define YT_ready function.
var YT_ready = (function() {
    var onReady_funcs = [], api_isReady = false;
    /* @param func function     Function to execute on ready
     * @param func Boolean      If true, all qeued functions are executed
     * @param b_before Boolean  If true, the func will added to the first
                                 position in the queue*/
    return function(func, b_before) {
        if (func === true) {
            api_isReady = true;
            while (onReady_funcs.length) {
                // Removes the first func from the array, and execute func
                onReady_funcs.shift()();
            }
        } else if (typeof func == "function") {
            if (api_isReady) func();
            else onReady_funcs[b_before?"unshift":"push"](func); 
        }
    }
})();
// This function will be called when the API is fully loaded
function onYouTubePlayerAPIReady() {YT_ready(true)}

// Load YouTube Frame API
(function() { // Closure, to not leak to the scope
  var s = document.createElement("script");
  s.src = (location.protocol == 'https:' ? 'https' : 'http') + "://www.youtube.com/player_api";
  var before = document.getElementsByTagName("script")[0];
  before.parentNode.insertBefore(s, before);
})();

// Previously, core functions were defined. Look ahead for the implementation:

var player; //Define a player object, to enable later function calls, without
            // having to create a new class instance again.

// Add function to execute when the API is ready
YT_ready(function(){
    var frameID = getFrameID("tabs2");
    if (frameID) { //If the frame exists
        player = new YT.Player(frameID, {
            events: {
                "onStateChange": stopCycle
            }
        });
    }
});

// Example: function stopCycle, bound to onStateChange
function stopCycle(event) {
    alert("onStateChange has fired!\nNew state:" + event.data);
}

If you want to invoke additional functions at a later point, e.g. mute a video, use:

player.mute();

• If you only have to call simple single-direction functions, it’s not necessary to use this code. Instead, use the function callPlayer as defined at this answer.
• If you want to implement this feature for multiple frames, simultaneously, have a look at this answer. Also includes a detailed explanation of getFrameID and YT_ready.