Cannot load server in an alias folder

Scenario:
I have the adsb web page loaded in an aliased virtual directory on my server (example.com/adsb/) which acts as a proxy to the http port of dump1090.

Expected Result:
The web page should load as normal and display the airplanes.

Actual Result:
The javascript in gmap.html tries to load "/data.json" instead of "data.json" which would end up being "adsb/json.data" and go through the virtual directory properly.

Fix:
I have confirmed that removing the leading "/" from "/data.json" resolves the problem and I have not observed any adverse effects.

A current work-around is to also proxy "/data.json" to the dump1090 port, but this adds extra complexity and the possibility of name clashes (especially being a generic filename).