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.

11,394 thoughts on “iframe automatic height adjustment using HTML5 cross domain web messaging

  1. Только вот странно что в трипе написано что пак был с 1гр ск а твой заказ это покупка а продажу у магазина от 5гр купить Мефедрон Бошки Марихуану Больше хороших отзывов чем плохих думаю магаз ровный. А проблемы которые возникают решаются навернВсе заказ пришел не было времени отписаться брали пробы в аське вежливыйконкретный все в срокипросил отправить в день перевода денег отправили шла ровно 4 дня как написанно на сайте веса точные не обманывают все порадовало консперация на высшем уровне правда расчитывал на лучшее качество мало держит консентрация 1 к 6-8 самая лутая.. Огромное спасибо магазину мир и процветание выбераю чемикал микс Всем мир друзья..

  2. Great insights on optimizing Instagram Ads! I’ve been testing creatives with different hooks and found short captions convert better. I’ll share more findings here: ppc company

  3. Sharing knowledge empowers others equipping them fully navigate complexities associated achieving desired outcomes positively impacting lives collectively uplifting spirits inspiring hope healing journeys undertaken successfully progressing forward Florida Workers Compensation

  4. Букмекерская контора Мелбет предлагает хорошо организованный сервис для пользования услугами оператора. Разнообразие ставок с неплохими коэффициентами сопровождается бонусными программами нацеленными на поддержание интересов клиентов. Получение бонусов от букмекера позволяет получить новый безболезненный опыт на ставках что особенно важно для новичков промокод melbet при регистрации. Однако предполагаем что снижение требований по отыгрышу бонусов сделали бы букмекера еще привлекательнее для игроков.

  5. If you’re dealing with a rat infestation, it’s crucial to address it quickly to prevent health risks and property damage. Effective rat removal techniques can make a significant difference in maintaining a safe and clean environment Pest control Puyallup

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>