Answers for "how to update the data in realtime database in firebase in js"

how to update the data in realtime database in firebase in js

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);
});