An example firebase wrapper

firebase.kt

@JsModule("firebase")
@JsNonModule

external interface FirebaseConfig {
    var apiKey: String
    var authDomain: String
    var databaseURL: String
    var projectId: String
    var storageBucket: String
    var messagingSenderId: String
    var appId: String
}

external interface Firebase {
    fun initializeApp(jsObject: FirebaseConfig): FirebaseApp
}

external interface FirebaseApp {
    fun firestore(): Firestore
}

external interface Firestore {
    fun batch(): Any
    fun collection(path: String): Any
    fun doc(path: String): Any
}

@JsName("firebase")
external val firebase : Firebase