Firestore web code sample gives invalid argument type

Question

I am trying out the new Firestore by Firebase. When I run the code sample from https://firebase.google.com/docs/firestore/manage-data/add-data?authuser=0, I am getting an error.

// Add a new document with a generated id.
db.collection("cities").add({
    name: "Tokyo",
    country: "Japan"
})
.then(function(docRef) {
    console.log("Document written with ID: ", docRef.id);
})
.catch(function(error) {
    console.error("Error adding document: ", error);
});

Exception caught: (FirebaseError) : Function CollectionReference.add() requires its first argument to be of type object, but it was: a custom Object object

Edit: Sorry I didnt mention I am using GWT and JSNI, it's working fine without gwt

Answer 1

Quick workaround

var city: any;
city = Object.assign({}, {
    name: "Tokyo",
    country: "Japan"
});
db.collection("cities").add(city)