Question

When you add a script tag with an src field pointing to a javascript file, the browser gets it and executes it.

What I am wondering is how does this process work. Does the file get fetched and then somehow eval()‘ed? Is it a mystical process that happens outside of the scope we have access? Or can we monitor/interfere this?

To explain what I want to achieve:
I want to give access to third parties to customize their page on my site by linking to their own javascript files. I want to be able to centrally log any errors that prevent those external scripts from loading (i.e. their server is down, parsing errors, whatever). Is it possible?

Thanks!

• Obviously there are other ways to solve this such as hosting their scripts on my server and giving them a way to update them, but I ‘m interested in knowing if my current approach is possible.

Answer 1

You can look at specific implementation in Firefox & Chromium sources with some grep magic, for your specific scenario I’d asynchronously subload those by inserting script tags on the fly and listening to global errors/events (eg window.onerror) from there.