javascript anonymous object in kotlin

Question

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 ...}

Answer 1

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
}

Answer 2

Here's a helper function to initialize an object with a lambda syntax

inline fun jsObject(init: dynamic.() -> Unit): dynamic {
    val o = js("{}")
    init(o)
    return o
}

Usage:

jsObject {
    foo = "bar"
    baz = 1
}

Emited javascript code

var o = {};
o.foo = 'bar';
o.baz = 1;

Answer 3

One more possible solution:

object {
        val `content-type` = "text/plain"
        val `content-length` = 50
}

It seems that it does not work anymore with escaped variable names.

Answer 4

I'm a Kotlin newbie (though not a newbie developer), I slightly extended answer from @bashor to something looks neater for keys which are valid Java identifiers, but still allows ones which aren't. I tested it with Kotlin 1.0.1.

@native("Object")
open class Object {
}

fun jsobject(init: dynamic.() -> Unit): dynamic {
    return (Object()).apply(init)
}

header = jsobject {
    validJavaIdentifier = 0.2
    this["content-type"] = "text/plain"
    this["content-length"] = 50
}