Facebook iOS Mobile Web JS SDK Error

Question

We already have Facebook working on our main desktop app without an issue. When I added the same setup code to our mobile site I received an error from the JavaScript SDK:

Answer 1

With all due respect, I believe that bokonic's answer is missing the point. The immediate reason of the message you're receiving is most likely javascript postMessage method. It is used to communicate your website with an object returned by window.open or an iframe's embedded website.

window.parent.postMessage(message, targetOrigin);

You might want to have a look at this article to see how it works.

According to MDN reference first argument of the postMessage method can be of any type. Still, Prior to Gecko 6.0 (Firefox 6.0 / Thunderbird 6.0 / SeaMonkey 2.3), the message parameter must be a string.

I tested the method on Chrome 28.0.1500.72 (latest version when writing this answer) and it works fine when passing an object but still throws the warning message to the console. I believe that facebook feels uncomfortable with passing some rich data as a string so they pass it as an object and simply doesn't care about the warning. Or, since there is a workaround (e.g. JSON.stringify), they have a bug they don't know about.