Assigning postMessage function to specific iframes

Question

How can I optimize the following postMessage functionality, so that it will attach the page to the correct iframe by id, and not by the location in the array window.frames[2]?

I'm using the following, which works:

var getFontFamily = function() {
      var el = document.getElementsByTagName("h1")[0];
      var cs = window.getComputedStyle(el, null);
      return cs.fontFamily;
  } 

window.addEventListener('load', function(){
    var data = getFontFamily("h1");

    window.frames[2].postMessage(data, 'http://localhost:3000/syndicatedPlayer/syndicatedPlayer.html');
    window.frames[3].postMessage(data, 'http://localhost:3000/syndicatedPlayer/syndicatedPlayer.html');

    console.log('Message sent -->');
});

but would like to optimize this code, so that I don't have to find which iframe to use on the page(it should apply the post message to id="frame1" and id="frame2", not based on a manually entered frame.

The iframes that have the id's:

<iframe id="frame1" style="width: 100%; height: 420px;" src="../syndicatedPlayer.html#videoUrl=http://video.mp4?" frameborder="0"></iframe>

<iframe id="frame2" style="width: 100%; height: 420px;" src="../syndicatedPlayer.html#videoUrl=http://video.mp4?" frameborder="0"></iframe>

One thought was the following, but this is not working:

function getFrameById(id) {
    for (var i = 0; i < window.length; i++) {
        if (window[i].frameElement.id === id) {
            console.log('found frame in index ' + i);
            return window[i];
        }
    }
    return null;
}

getFrameById('frame1').addEventListener("load", function (e) {
    var data = getFontFamily("h1");
});
getFrameById('frame1').postMessage(data, 
'http://jsfiddle.net/mattography/tmhfv2ft/1/show');
console.log('Message sent -->');

getFrameById('frame2').addEventListener("load", function (e) {
 var data = getFontFamily("h1");
    });
getFrameById('frame2').postMessage(data,     
'http://jsfiddle.net/mattography/tmhfv2ft/1/show');
    console.log('Message sent -->');

Example: jsfiddle