asciinema.org/app/views/asciicasts/show.js.erb

// asciinema.org - embeddable player

(function() {
  function receiveSize(e) {
    if (e.origin === document.location.protocol + "//<%= request.host %>") {
      var event = e.data[0];
      var data  = e.data[1];
      if (event == 'asciicast:size' && data.id == <%= @asciicast.id %>) {
        var player = document.getElementById("asciicast-iframe-<%= @asciicast.id %>");
        if (player) {
          player.style.width  = data.width;
          player.style.height = data.height;
        }
      }
    }
  }

  function insertAfter(referenceNode, newNode) {
    referenceNode.parentNode.insertBefore(newNode, referenceNode.nextSibling);
  }

  var scriptTag = document.getElementById("asciicast-<%= @asciicast.id %>");

  if (scriptTag) {
    window.addEventListener("message", receiveSize, false);
    var container = document.createElement('div');
    container.className = 'asciicast';
    container.style.display = 'block';
    container.style.float = 'none';
    container.style.overflow = 'hidden';
    container.style.padding = '0';
    insertAfter(scriptTag, container);
    var containerWidth = container.offsetWidth;
    container.innerHTML = '<iframe src="http://<%= request.host_with_port %>/a/<%= @asciicast.id %>/raw?container_width=' + containerWidth + '" name="asciicast-iframe-<%= @asciicast.id %>" id="asciicast-iframe-<%= @asciicast.id %>" width="600" height="300" scrolling="no" marginheight="0" marginwidth="0" frameborder="0" style="display: block; float: none; visibility: hidden;" onload="this.style.visibility=\'visible\';"></iframe>';
  }
})();