iframe automatic height adjustment using HTML5 cross domain web messaging

Posted on by

Yesterday I was working on a site that needed an iframe embedded in the page whose content came from a completely different domain. I try to steer clear of iframes at all costs normally so forgive me if what I’m about to say is pretty obvious.

I didn’t want the content in the iframe to appear as though it was in an iframe, so obviously I stripped off all the default browser styles…well, the border. I wanted the iframe to be as high as the content it was containing so that no scroll bars would appear.

So what I did was just give the iframe a height, however when the user navigated to a different page within the iframe, the height I had previously set was too big or too small.

I instantly thought “right, JavaScript will sort this out for me!” and proceeded to quickly code up a function that would inspect the scrollHeight of the content in the iframe and adjust the iframe height accordingly.

No! Said cross domain policy. I had momentarily forgotten all about that. Since the iframe content came from a different domain, I wasn’t allowed to access the document object of the iframe (or vice versa).

Here is how not to do it

Firefox says “Error: Permission denied to access property ‘document’” and other browsers similar.

I started searching for some kind of workaround.  Of course there isn’t really one…except I did find an interesting hack for Firefox. Which is – an iframe document can alter the url fragment of the parent window’s location object! ha madness.

The idea is that the document in the iframe alters the url fragment to read:

http://freestyle-developments.co.uk/blog/?p=150#138

Where 138 is the height of the iframe document (obviously you could be a bit more fancy and send other parameters and name them e.g #height:138 but for simplicity I’ve just set the value). The parent then reads this value and sets the iframe height accordingly:

var iFrameHeight = parseInt(location.hash.replace('#', ''));

So…yeah, that’s pretty interesting, but not really a solution. Check out the example implementation here.

Anyway, what to do? HTML5 web messaging to the rescue! Sweet! HTML5 web messaging is cross domain messaging done right. Not only does the messenger choose who should receive messages, but the recipient also chooses who to receive messages from.

The idea is that after the iframe document has loaded, it sends a message to the parent window telling it what it’s scrollHeight is. The parent listens for messages, and sets the height of the iframe when it receives a message.

A couple of things to note:

  1. There has to be communication between the two documents. i.e. the document on the external domain needs to actively send this message. Which can be a complete show stopper if you have no control over the document on the external domain
  2. This isn’t going to work on IE < 9. I tested the implementation linked below is working on FireFox 4 (Beta 7), Safari 5.0.2, Chrome 8, Opera 10.63 and Internet Explorer 9 Platform Preview 7. Which is a pretty good spread to be honest

Check out the example HTML5 web messaging implementation here.

21,166 thoughts on “iframe automatic height adjustment using HTML5 cross domain web messaging”

  11. Раньше розницей занимались благодаря вашему опытусейчас время другоестабильная честная работа купить скорость кокаин мефедрон гашиш 2. Был подобный заказ и нас спутали.часть покупателей устраивает продавцы тоже не жалуется. В чем проблема? нет терпения – идите в другие шопы.

  20. I absolutely love how jewelry can change an entire outfit! It’s fantastic how a simple piece can add a lot sophistication and personality. Have you ever thought about customizing your own jewelry? It can produce a genuinely special declaration piece buy gold Denver co

  27. Когда мгновенный доступ к ставкам становится таким же естественным, как проверка мессенджера, мобильное приложение 1Win превращается в незаменимый инструмент для активных пользователей. По ссылке https://t.me/s/win1win_skachat_na_android можно скачать официальную версию 1win для Android и получить в кармане полный функционал букмекерской платформы: от линии и лайв-ставок до личного кабинета и истории операций. Удобный интерфейс, адаптированный под смартфоны, быстрый отклик и возможность следить за событиями в любом месте делают приложение логичным выбором для тех, кто ценит скорость, контроль и комфорт в мире онлайн-ставок.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>