Naming Dynamically Created iframes

For the past year, I have been working on a web application that relies heavily on inline frames (aka iframes). During the course of development, we have run into some interesting issues and I thought I would record some of these for posterity.

The W3C specification for the IFRAME element states the following document type definition:

<!ELEMENT IFRAME - - (%flow;)*         -- inline subwindow -->
<!ATTLIST IFRAME
  %coreattrs;                          -- id, class, style, title --
  longdesc    %URI;          #IMPLIED  -- link to long description
                                          (complements title) --
  name        CDATA          #IMPLIED  -- name of frame for targetting --
  src         %URI;          #IMPLIED  -- source of frame content --
  frameborder (1|0)          1         -- request frame borders? --
  marginwidth %Pixels;       #IMPLIED  -- margin widths in pixels --
  marginheight %Pixels;      #IMPLIED  -- margin height in pixels --
  scrolling   (yes|no|auto)  auto      -- scrollbar or none --
  align       %IAlign;       #IMPLIED  -- vertical or horizontal alignment --
  height      %Length;       #IMPLIED  -- frame height --
  width       %Length;       #IMPLIED  -- frame width --
  >

The key thing I’m interested in here is the name attribute. Our particular application allows iframes to fire events which are then caught by the parent window. In order to identify the source of these events, the iframes send along their name (accessed via window.name).

If you have an iframe like the following in your web page:

<iframe frameborder="0" name="bob" src="/some-page"></iframe>

And /some-page contains the following HTML:

<!DOCTYPE html>
<title>Test</title>
<script>
document.write('My name is ' + window.name);
</script>

Then the iframe should output the following:

My name is bob

Here’s that in action:

However, if you are dynamically creating iframes with JavaScript (perhaps to avoid BFCache bugs) then you may run into some issues where window.name is undefined in Internet Explorer 6 and 7.

Specifically, if you create an iframe and set its name like so:

<script>
(function () {
    var iframe = document.createElement('iframe');
    iframe.src = '/some-page';
    iframe.name = 'bob';
    document.body.appendChild(iframe);
}());
</script>

Then /some-page will report the following:

My name is

Again, a live demonstration (note that this will only be broken in Internet Explorer):

The same will occur if you use jQuery:

<script>
$(function () {
  $('<iframe/>', {
    src: '/some-page',
    name: 'bob'
  }).appendTo(document.body);
});
</script>

The issue arises because the name of an iframe cannot be changed in Internet Explorer, much like the type attribute on input (there is a caveat in the jQuery documentation about the type issue when creating elements).

This means that you must set the name attribute on creation of the element, not afterwards.

With jQuery, it’s a case of doing the following:

<script>
$(function () {
  $('<iframe name="bob"></iframe>').attr({
    src: '/some-page'
  }).appendTo(document.body);
});
</script>

With pure JavaScript it is slightly trickier as you can no longer use document.createElement. However, you can create a temporary container element (say, a div), and then modify that element’s innerHTML to create your iframe with its name from the beginning. You can then take your newly created iframe and insert that directly into the DOM (without ever inserting your temporary div) like so:

<script>
(function () {
  var temp = document.createElement('div');
  temp.innerHTML = '<iframe name="bob" src="/some-page"></iframe>';
  document.body.appendChild(temp.firstChild);
}());
</script>

(This is actually what jQuery does internally in the prior example.)

In this way, all browsers should now correctly report:

My name is bob

And a live demonstration: