You cannot always do a post call on page unload.

Answering my own question because of a couple things I discovered in my research:

• There's no such thing as "check if the page was not left after preventdefault was called."

• Also, this is not what preventdefault is for. The get call is made no matter what, even if you don't leave the page.

• beforeUnload may work all the time locally, but not on the server. Listen to what everybody says, it's not worth it.

• However, pageHide does almost everything you want successfully. In page navigation/refresh, it will do the API call, if you put "keepalive: true" in your request options.