How to include file in NodeJS SOAP request

I am using the MERN stack and one of our requirements is to hit a SOAP web service from NodeJS. Part of this SOAP call includes a file upload. I have been using node-soap package (https://github.com/vpulim/node-soap). Is there an additional NPM package that I can use for this purpose, that is specifically to include a file in a SOAP request? As a backup how does SOAP handle files? Is there some way I can hack this, like convert it to base64 or something like that first? Any help is greatly appreciated. Versions below.

node -v v6.10.2
npm -v 3.10.10
soap@0.19.0
│ ├── compress@0.99.0
│ ├─┬ concat-stream@1.6.0

via david