Web Workers was born for this purpose. http://www.whatwg.org/specs/web-workers/current-work/ http://www.whatwg.org/specs/web-workers/current-work/ (and it woul

Web Workers was born for this purpose. http://www.whatwg.org/specs/web-workers/current-work/ http://www.whatwg.org/specs/web-workers/current-work/ (and it would be non-trivial to detect this kind of code in Javascript).