javascript - iFrame isolation

Question

Just a thought, but would using an IFRAME over a DIV essentially make that element isolated from the window in a way that slow scripts running in the IFRAME wouldn't affect the other frames/window?

Answer 1

Yes for the first part, an iframe will "sort-of" isolate your window from the script in the iframe. However, the parent window can still be accessed via window.parent.

For the second part: No, it will not make it so slow scripts in the iframe won't affect other frames/windows. Your main window object and its child nodes all run in the same thread. JavaScript is single threaded [Ignore webworkers in this case, you can't pass dom elements between them anyway], so the only reason you can access the parent-window/child-iframe's window object is because they're on the same thread.

To provide a quick example:

• Create a page called main.html
• In that page, have an iframe src="iframe.html"
• Next to the iframe, have a button with whatever text you want, I don't care.
• In iframe.html, window.onload = function(){ while(1){} };
• Access iframe.html. You'll notice that when you put your mouse cursor over the button, it doesn't respond/redraw. This is because the browser is frozen.

Source:
I tried getting multithreading like this too. Learned the hard way =)