On using %5C in .npmrc which turns into "/" instead of "\"

Question

Long story short: I'm behind a proxy and would require setting up my .npmrc to be able to "npm install ". But my username includes the domain and a "\" (ex. domain\username) which in multiple places says I'd need the encoded "%5C". So when I try to set up the config by:

npm config set proxy "http://<domain>%5C<username>:<password>@http://<proxy>:<port>"

Then run npm config get proxy: The %5C is always there instead of replacing with a "\".

ex: http://domain%5Cusername:password@http//proxy:port

And as with other posts when I do use the "\" it's replaced by "/" instead.

Any insight and how to get this to show up correctly as "\" in the .npmrc file would be much appreciated.