Really cool! In my young days I had fun with js alerts in certain forums. It's incredible modern browsers still suffer these problems. I have managed to freeze my computer with resource intensive js scripts that required a forced power off, but I never save the code of these bugs. With the latest Ubuntu my machine used to freeze when opening Gmail in Firefox, I started suspecting some kind of sabotage on Firefox, but never managed to find the actual cause.
I was unable to stop my own creation and had to ctrl-alt-del kill the browser - except that when I started the browser again, it went back to the last opened window.
It took a bit of work regaining control. I wish I had saved the code, although it wouldn't work today since browsers restrict window open/close these days.