The most performant way that I’ve found to parse JSON using KotlinJS is to use native

JSON.parse

to produce a

dynamic

, and then

unsafeCast

it to an exported class. This works great, and allows for code sharing across targets (contrasted with

external interface

). This looks like: The problem is that you end up with an incomplete instance of the class, and so if there are extension functions defined on the class, they’ll crash at runtime. I would like to define a

JsExport

class that cannot receive extensions so that users of the class don’t accidentally write code that will crash at runtime!