iframe automatic height adjustment using HTML5 cross domain web messaging

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.

11,786 thoughts on “iframe automatic height adjustment using HTML5 cross domain web messaging

  1. Тем, кто ценит практичность и долговечность, подойдут новогодние композиции из искусственных цветов: они годами сохраняют форму и цвет, не требуют ухода и всегда выглядят как только что созданные. На странице https://www.florion.ru/catalog/novogodnie-kompozicii-iz-iskusstvennyh-cvetov интернет-магазина «Флорион» собраны стильные варианты для дома, офиса, витрины или праздничной фотозоны — от лаконичных современных композиций до классических новогодних решений. Такой декор удобно хранить и использовать из года в год, создавая узнаваемый фирменный новогодний стиль вашего пространства.

  2. It feels reassuring knowing there exists such supportive environments aimed strictly towards enhancing confidence levels amongst individuals navigating through journeys commencing right here within familiar grounds belonging solely within quaint little Clear Braces

  3. Обратите внимание ТС отказывается работать с ГАРАНТОМ хоть и магазин древний и проверенный но хочется спать спокойно АДМИНЫ ОБРАТИТЕ ВНИМАНИЕ ПОРА КАК ТО ИЗМЕНИТЬ РЕЖИМ РАБОТЫ ГАРАНТА. СДЕЛКИ ПРОВОДИТЬ ОБЯЗАТЕЛЬНО ТОЛЬКО ЧЕРЕЗ ГАРАНТА https://teploceramic.biz Товар нормальный. В этот понедельник оплатил ещё ждувсё как всегда быстро чётко без всякой канители качество как всегда радует спасибо команде за работуВЫ ЛУЧШИЕ

  4. I found your breakdown incredibly clear. Your advice on panel upgrades is critical for local Mystic properties. It might be useful to discuss solar integration for local homes? Additional insights can be found here: electrical repair Mystic CT .

  5. I accept as true with fostering independence step by step aids children’s trust tiers immensely–these early steps pave pathways closer to long term achievements forward!!! ### anyKeyWord### private child care

  6. If you cook dinner jasmine or basmati quite often, you’ll desire adjustable settings. I realized tons from the roundup on top rice makers about which versions care for exclusive grains first-class.

  7. 1. Wow, ik ben echt geschrokken van dit artikel! Had geen idee dat dit zo’n groot probleem kon worden. Mijn dochter zit ook veel op dat soort apps, maar vanaf nu houd ik het veel beter in de gaten. Thanks dat jullie dit delen!

    2 Bekijk deze site

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>