jQuery Forum

You would have the same problem with native XHR or native fetch.

If you are running without a server, Safari allows cross domain Ajax. Chrome and firefox do not. but there is an option for each that allows cross domain when served without a server (file://)

The application is a lightweight network monitoring app in a web page. The browser periodically issues the ajax() call to various addresses to determine if the host responds or not. Either way, the browser updates its page to show the current state of the devices it has queried. (If you're terminally curious, you can check http://TestMyInter.net )

Getting any kind of error response (even a CORS error) is good: it's an indication that the other end is present - that's all I care about. A timeout, on the other hand, shows that the device is simply not responding. 

Some of the queries are made to hosts that I already know are down/unresponsive. So I'm trying to distinguish two kinds of timeouts:

I wrote to this forum to see if there's someone who knows the deep underpinnings of ajax(), and how Chrome, Firefox, and Safari might handle it differently.

Any thoughts? Any ideas where else I could post this question? Many thanks!

I run beta everything on my Mac as well. 

TL;DR - The current code issues a XMLHttpRequest() with timeout=0, and uses a separate setTimeout() to abort the request if it has gone long enough. Read the rest of the code to get more details.