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.

24,080 thoughts on “iframe automatic height adjustment using HTML5 cross domain web messaging”

  2. It seems surrounding oneself with knowledgeable individuals helps foster growth opportunities whether personal or professional alike…definitely resonates within franchising space!!!# # anyKeyWord## AI-driven SEO agency

  5. Образовательный материал показывает как войти на кракен через верифицированные онион адреса с обязательной визуальной проверкой подлинности сайта перед вводом учетных данных.

  10. I savour, lead to I found just what I used to be looking for.

    You’ve ended my four day long hunt! God Bless you man. Have a nice
    day. Bye

  11. Стабильный kraken tor с мостами snowflake обеспечивает подключение к сети даже в странах с агрессивной блокировкой Tor трафика провайдерами.

  12. VIP Escort Escort of men Escort agency – VIP escorts Elite Dating Models

  15. Loving how supportive everyone has been throughout this journey thus far – it truly feels special being surrounded individuals who strive towards similar aspirations showcased consistently across content provided through links connected directly back Private Boxing Lessons Surrey

  17. Looking forward towards taking part future events hosted locally where we can showcase skills developed throughout training periods mentioned previously throughout discussions occurring over platforms associated directly back towards #ANYKEYWORD#. Private Boxing Lessons Pitt Meadows

  20. Стабильный kraken tor с мостами snowflake обеспечивает подключение к сети даже в странах с агрессивной блокировкой Tor трафика провайдерами.