How to detect if Javascript is running in an cross-domain IFrame in Opera?

Question

How to detect if JavaScript is running in an cross-domain IFrame in Opera? If I try to test if(typeof iframe.parent.document === 'undefined') Opera 12 just seems to give "Unhandled Error: Security error: attempted to read protected " which cannot be caught in code thus breaking execution.

Answer 1

You can't. However if your objective is to prevent someone on a different domain from embedding your page in an iframe, there is a http header you can send to prevent this.

https://developer.mozilla.org/en-US/docs/The_X-FRAME-OPTIONS_response_header

It's supported by most modern browsers. It allows you to specify which sites are allowed to embed your page in an iframe.