I wrote a content script to access DOM content of a web page.I am able to access the DOM content but when i try to access one iframe contentwindow in that page it is saying as undefined.

It is like document.getElementById('iframe') is giving me the iframe but when i try to access document.getElementById('iframe').contentwindow it is saying undefined.

I want to access a script running in that document.

Thanks

You can not access contentWindow because it contains page functions, and for security reason all page functions is not accessible.

Even if modify an element's onClick then fire click event, onClick won't be triggered; so does origin onClick event if exist.

You can not access page functions.