How do I point NW expression to desktop?

I got this js expression that saves a snapshot on my user folder:

"var fs = require('fs');fs['writeFileSync']('" &replace(NodeWebkit.UserFolder & "screenshot" & ".png","\","\\")& "','" &CanvasSnapshot& "'.split(',')[1], {'encoding': 'base64'});"

I used NodeWebkit.UserFolder for saving it on my User folder, but i need it to be on the desktop, what should i add to that?

For those who want an answer see this post

https://www.scirra.com/forum/this-is-driving-me-crazy_t152226