Using npm behind corporate proxy .pac

I've just had a very similar problem, where I couldn't get npm to work behind our proxy server.

My username is of the form "domain\username" - including the slash in the proxy configuration resulted in a forward slash appearing. So entering this:

npm config set proxy "http://domain\username:password@servername:port/"

then running this npm config get proxy returns this: http://domain/username:password@servername:port/

Therefore to fix the problem I instead URL encoded the backslash, so entered this:

npm config set proxy "http://domain%5Cusername:password@servername:port/"

and with this the proxy access was fixed.

Look for the url of the pac file in internet explorer lan settings and download the pac file from the URL configured. The pac file is just a javascript file with a function named FindProxyForURL which returns different proxy hosts in different scenarios.

Try to find a host in that pac file which you think is for general web traffic and plug it into .npmrc in C:\Users\<username>\.npmrc

proxy=http://<username>:<pass>@proxyhost:<port>
https-proxy=http://<uname>:<pass>@proxyhost:<port>

Even though you may login with your domain and username on your corporate machine, It is highly possible that the user active directory domain name is not required for the proxy, only the username and password (which may be different than your Active Directory login)

Don't forget to fiddle with escaping special password characters.