@Vladimir: thank you that I did find the URL from the referenced page.
However, when I used the URL pattern plus xsjs file name, plus parameters to either POST or GET, none of them works. HTTPS returns 200 but it is the logon page of HANA cloud and not the result that I expected to see. For POST data to HANA database, the data was not added to the DB table, either.
I cannot trigger the HANA log file to see whether the https calls really reach HANA because of insufficient administration right.
Additionally, how do we debug HANA XS in the HANA cloud? I know the code works because I migrated working code from an SAP internal HANA development system.
Without all these, it seems impossible to develop XS application on this HANA cloud.