javascript - Prevent F11 keydown on iframes on page? -

i have several iframes in popup window each target of form posts different sites.

i have following prevent f11 keydown on document:

document.onkeydown = function () {     if (event.keycode == 122) {          event.keycode = 0;          return false;     }  } 

goal: prevent user viewing url before , after iframe loads.

question: there better alternative meeting goal instead of handling keydown event? possible handle such event iframe holds contents of domain? possible still listen , prevent onkey events on iframe eventhough iframes incapable of having onkey attributes?

the solution should vanilla js or use little jquery references possible.