typically you use some sort of framework to parse and generate the xml into the objects that your chosen programming language uses

Is there a recommended Javascript framework that I could use? If not, I have no problem building something to fit our needs. I'm just having a hard time determining how the SOAP payload for getting all Custom Item Fields would look like.

your choice is https://github.com/vpulim/node-soap

I see. So in general, I wouldn't be creating those payloads manually?

its not impossible, but it largely defeats the intentions behind how structured soap is

I see. I'll take a look at this library and I'll let you know how it goes. Thanks!

at best, i usually see using something like using soap-ui to generate a working request and then copying that in your code

Thats kind of where I was at

Soap ui usually can generate you the request