I solved the issue with that implementation: 

// declarations
@JsModule("kafkajs")
external object kafka {
    fun consumer(options: ConsumerOptions): dynamic
}

external interface ConsumerOptions {
    var groupID: String
}

// code
fun createConsumer(): dynamic {
val options: ConsumerOptions = js("({})")
options.groupID = "test-group"
return kafka.consumer(options)
}