global interceptor for third party scripts who redirect

Question

One of the scripts to an offsite third party widget broke during execution and redirected all traffic on my homepage to theirs.

Since I can't kill them, I'm either going to have to kill the script, or figure out a way to kill any attempt a third party JavaScript might make to redirect the browser. The most promising events I've found are .unload() and window.onbeforeunload, and my idea is to hopefully inspect the GET request and then validate the URL as not matching any of the valid links on my page, that's no problem except that I don't know how to get the event's GET value considering it's not bound to any clicks or action on the page, but a bogus something or other in a third party's .js?

Anybody have luck working out a solution to something like this?

Answer 1

There is no way that I know of to intercept all possible places that 3rd party javascript might set window.location causing a redirection and preflight it. It is not a method, it's just a property set to there's no method to replace/override.

The page unload event just gives you a chance to ask the user if they really want to leave this page, but it has no access to what the new page destination is.

The only thing I can think of is to keep a global variable that contains a boolean that defaults to false. In all possible places that you might change pages in your own code, you set that boolean to true. In the onbeforeunload handler, you check that global variable to see whether it's something your code did or not. If it is not something your code did, you return a message from onbeforeunload so the user will be prompted for whether they really want to leave or not. But, you can't prevent it (this is a browser design on purpose). If they say yes to the prompt, they will leave the page to the new destination.

If you or someone else could actually figure out why the 3rd party was inintentionally causing the redirection, then perhaps you could concentrate on making sure that condition doesn't happen again, but you've given us no info on that so we can't really help with that.