javascript anonymous object in kotlin

how to create JavaScript anonymous object in kotlin? i want to create exactly this object to be passed to nodejs app

var header = {“content-type”:”text/plain” , “content-length” : 50 ...}

Possible solutions:

1) with js function:

val header = js("({'content-type':'text/plain' , 'content-length' : 50 ...})") 

note: the parentheses are mandatory

2) with dynamic:

val d: dynamic = object{}
d["content-type"] = "text/plain"
d["content-length"] = 50

3) with js + dynamic:

val d = js("({})")
d["content-type"] = "text/plain"
d["content-length"] = 50

4) with native declaration:

native
class Object {
  nativeGetter
  fun get(prop: String): dynamic = noImpl

  nativeSetter
  fun set(prop: String, value: dynamic) {}
}

fun main(args : Array<String>) {
  var o = Object()
  o["content-type"] = "text/plain"
  o["content-length"] = 50
}