Our client needs to upload their database to the server and it looks like it is impossible to create a SFTP connection in JavaScript and FTP is not secure (and FTPS has issues).
Is using a HTTPS connection and posting a multipart form a viable alternative to SFTP?
Is HTTPS upload over post form multpart as secure as SFTP?
If you have up-to-date browser, up-to-date server (setup to accept reasonable algorithms) and reasonable certificate (that validates) the HTTPS is secure the same way as SFTP is (using reasonable algorithms in SSH and properly validating host keys).
Transferring files is secure as transferring any other confidential information using HTTPS (the banks/card payment services do that all the time).