How to serialize a Map to JSON string via JSON.stringify in kotlin JS?

Question

My example code is below:

fun main(args: Array<String>) {
    val testData = mapOf<String, Any>(
        "name" to "albert",
        "age" to 26,
        "work" to listOf("1", "2", "3")
    )

    var value = JSON.stringify(testData, { _, value -> value.toString() }, 2)

    println(value)
}

The result is "{name=albert, age=26, work=[1, 2, 3]}". Seems it misses all the double quotes around the property name and string value.

I'm using KotlinJS rather than Kotlin

So, how to solve this?

Answer 1

This answer comes a few years after the previous accepted answer, but I (who am new to Kotlin) ran into this same problem, and figured out a nice way to achieve this.

1. Assume you have a populated Map
2. Create an empty js object (seems hacky to me, but this is Kotlin to JS)
3. iterate over the your map's "toList" method which provides a Pair
4. insert each pair into js object
5. grab the js JSON api

6. and call "stringify" providing your js object. Remember to "toString" at the end

   val data: Map<String, Any?> = mapOf() // 1
   val export = js("{}") // 2
   for (pair: Pair<String, Any?> in data.toList()) { // 3
       export[pair.first] = pair.second // 4
   }
   val jsoner = js("JSON") // 5
   return jsoner.stringify(export).toString() // 6
   

Answer 2

If you wish to simply retrieve a valid JSON string from a Kotlin Map, you can do so using kotlinx.serialization.json:

Json.encodeToString(map)

If you would like to pretty stringify a Kotlin Map, which can be displayed as a pretty JSON in a <pre> tag, you can do:

val jsonString = Json.encodeToString(map)            // 1
val jsonObject = JSON.parse<JsonObject>(jsonString)  // 2
return JSON.stringify(jsonObject, null, 2)           // 3

1. Serialize the map to a JSON string using Kotlin serialization
2. Parse the JSON string to a Javascript object
3. Pretty stringify the Javascript object