I think iframe is used for security reasons, see https://stackoverflow.com/questions/8004001/how-does-jsfiddle-allow-and-execute-user-defined-javascript-without

I think iframe is used for security reasons, see https://stackoverflow.com/questions/8004001/how-does-jsfiddle-allow-and-execute-user-defined-javascript-without-being-danger https://stackoverflow.com/questions/8004001/how-does-jsfiddl... it allows third party scripts to run in a contained environment.