https://mtsepkov.org/extensions/CustisScripts/msgresize.js

1//HTML5 postMessage usage to ease embedding iframes from different domains
2//The page loaded in iframe needs to send postMessage("resize(w=WIDTH;h=HEIGHT)") to be resized.
3//Works in IE8+, FF3+, Opera 9.5+ and Chrome.
4
5var msgResize = function(e)
6{
7  var m = /resize\(w=(\d+);h=(\d+)\)/.exec(e.data);
8  if (m)
9  {
10    var f = document.getElementsByTagName('iframe');
11    for (var i = 0; i < f.length; i++)
12    {
13      if (f[i].contentWindow == e.source)
14      {
15        f[i].style.width = m[1]+'px';
16        f[i].style.height = m[2]+'px';
17        break;
18      }
19    }
20  }
21};
22
23if (window.addEventListener)
24    window.addEventListener('message', msgResize, false);
25else if (window.attachEvent)
26    window.attachEvent('onmessage', msgResize);