Yeah. I would have this env var inside my reverse proxy to have it 12-factor app compatible. And I guess your solution as well? And you have some templating mec

Yeah. I would have this env var inside my reverse proxy to have it 12-factor app compatible. And I guess your solution as well? And you have some templating mechanism to replace the absolute variable on the fly? I would use a mix of your solution, i.e. allow the Java script client to be configured with either absolute or relative urls in case one needs to point the client elsewhere + reverse proxy