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 ...}
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8 Answers
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
}
3 Comments
John Abraham
thanks for quick reply first solution may work but it is not flexible i mean it is hard coded value and i am getting some errors as well you can check it. 2nd solution creates Kotlin.createObject(.....) on javascript side i can't pass this to node.js this doesn't work
birgersp
2017 calling, trying to do the same as OP. is this answer outdated?
bashor
@gromit190 the answer looks like actual, please let me know if you have any problem with it.
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;
3 Comments
Robbie Cronin
this is the only one that worked for me, lifesaver!
iHad 169
The return Type can "dynamic" to "Json". e.g. inline fun jsObject(init: dynamic.() -> Unit): Json {} This will more than safe.
ayitinya
using this in kotlin/wasm, i get dynamic not supported in this context
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.
2 Comments
Jayson Minard
is this "possible" or does it work and do the same thing?
Sharp
Thanks @JaysonMinard, I fixed my answer.
In my Kotlin/JS + React project I have written an adapter for a library that accepts an anonymous configuration object through the constructor. After searching for a while I found a solution using kotlin.js.json
val options = json(
"position" to "top-right",
"durations" to json(
"global" to 20000
)
)
Comments
Here is another solution:
Define the following helper function
fun jsObject(vararg pairs: Pair<Any, Any>): dynamic {
val result = js("({})")
for ((key, value) in pairs) {
result[key] = value
}
return result
}
You can then use it as follows
val header = jsObject("content-type" to "text/plain", "content-length" to 50)
Comments
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.
@JsName("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
}
It is possible to transform a regular Kotlin object into a JavaScript anonymous object using JavaScript's Object.assign(). This allows you to stay in pure Kotlin and in type-safety as long as possible. So:
fun Any.toJsObject(): dynamic {
val thisArg = this // Allows use in js() function
return js("Object.assign({},thisArg)")
}
val anObject = object { val a = "a" } // Or use a regular class
console.log( anObject.toJsObject().a ) // logs "a"
