javascript - Difference between get() and onSnapshot() in Cloud Firestore

Question

I am reading some data from Firebase's Cloud Firestore but I've seen several ways to do it. The example I saw used the get and onSnapshot function like this:

db.collection("cities").doc("SF")
 .onSnapshot(doc => {
      console.log(doc.data());
 });

or this

var docRef = db.collection("cities").doc("SF");

docRef.get().then(doc => {
    if (doc.exists) {
         console.log("Document data:", doc.data());
    } else {
         console.log("No such document!");
    }
}).catch(function(error) {
   console.log("Error getting document:", error);
        });

Is there any difference between them?

Answer 1

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