If you type while(true){} in a notebook only the iframe will break (and usually your browser will prompt you after a while to kill it). When you do only the iframe is no longer functional.
I don't think there's an elegant way to solve it any differently in the browser.
[0]: https://starboard.gg
What I'm getting at is that these browser notebooks try to get at the desire and feeling for rapid exploration and iteration. Losing context by having a crashing logic error is a massive blow to that ideal.
I'm not saying that your or anyone elses product is only for "rapid prototyping" but it's still true that larger projects could be bit by the same errors. When I crash my native code I C-c and I'm back in an instant. When I crash browser notebook code I lose a bit of time and unsaved code. I crash browsers often in creative coding where I write many loops and don't always do them right.
It may also be that my chrome and firefox experience on linus is worse than standard, I don't know. But I have crashed my entire browser in chrome when using observable, and I thought that wasn't supposed to be possible.
Browsers will complain against code running for too long without interruption though.
Wow, that seems hard to do. One would need to take a lot of things in account, including recursive calls, asynchronous functions / calls and, indeed, even long strings of instructions that are not necessarily part of a loop or recursive calls.
Would a transform that adds the check between every JS instructions where it is possible theoretically solve the problem? is there a solution that does not slow down the code too much and interrupts the code within an acceptable margin?