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.

20,431 thoughts on “iframe automatic height adjustment using HTML5 cross domain web messaging”

  8. This message highlights specifically what families worry about: depend on and openness. We located clear responses through senior care when choosing assisted living.

  12. Le bonus de bienvenue 1xBet actuel peut atteindre 1 750 et inclut 150 tours gratuits pour la categorie casino credites directement sur le compte de jeu. Ces fonds peuvent etre utilises pour les mises des le depot initial notamment sur les machines a sous specifiees par le bookmaker. Un remboursement partiel de 30 sur les pertes peut etre attribue apres la periode de bienvenue. Pour en savoir plus sur le code promo 1xBet casino en ligne consultez ce lien : https://jerezlecam.com/pag/le_code_promo_1xbet_bonus.html

  23. Nếu bạn chưa thử cá cược tại đây thì hãy đăng ký ngay hôm nay để khám phá thế giới giải trí mới mẻ nhé!! ### HAYBET

  32. Hệ thống thanh toán trên hay88 rất linh hoạt và nhanh chóng, thật sự phù hợp với nhu cầu sử dụng hiện đại ngày nay! hay88

  41. Your takeaways relating to leveraging files analytics tell strategic decisions made quintessential fantastically navigating complicated environments ruled disruptive technologies moving person behaviors call for responsiveness agility velocity Brisbane SEO consultant

  47. escort agency VIP Escort Elite girls for escort VIP models

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>