Promise.then().catch(); Example

jspromise1_Promise.then().catch().js

// https://firebase.google.com/docs/firestore/quickstart

const userPromise = db.doc("user/" + uid).get().then(doc => {
  if (doc.exists) {
    console.log("User data:", doc.data());
    // use fetched data, for example in setState()
  } else {
    console.warn("No user data.");
  }
}).catch(error => {
    console.log("Error getting user data:", error);
});