I figured out how to do this. [yglukhov's
jsbind](https://github.com/yglukhov/jsbind) worked like a charm to help with
this. Thanks for the awesome library!
Here is a simple to get & set the height of a <div> in Nim.
import dom
import jsbind
type CSSStyleDeclaration* = ref object of JSObj
proc cssText*(cssSD: CSSStyleDeclaration): cstring {.jsimportProp.}
proc length*(cssSD: CSSStyleDeclaration): int {.jsimportProp.}
proc getComputedStyle*(w: Window; element: Element; pseudoElt:
Element=nil): CSSStyleDeclaration {.jsimport.}
proc getPropertyValue*(cssSD: CSSStyleDeclaration; property: cstring):
cstring {.jsimport.}
# Main Program
proc main() =
var
content = querySelector("#content")
cStyle = window.getComputedStyle(content)
content.innerHTML = cStyle.getPropertyValue("height") # e.g. will say
something like "51.2px"
content.style.height = "800px"