# Firebase 9 - Firestore Method Cheat Sheet

###### _6 min read_

[](https://code.build/u/86qJ3nXSvhBPUbmdaMwUeb/jdgamble555)

Mutations
---------

    // add doc
    await setDoc(doc(db, "pathname"), data);
    // upsert doc
    await setDoc(doc(db, "pathname"), data, { merge: true });
    // update doc
    await updateDoc(doc(db, "pathname"), data);
    // add item to array
    await updateDoc(doc(db, "pathname"), { arrayname: arrayUnion("new value") });
    // remove item from array
    await updateDoc(doc(db, "pathname"), { arrayname: arrayRemove("old value") });
    // increment a number
    await updateDoc(doc(db, "pathname"), { counter: increment(1) });
    // decrement a number
    await updateDoc(doc(db, "pathname"), { counter: increment(-1) });
    // delete a doc
    await deleteDoc(doc(db, "pathname"));
    // create an id
    const id = doc(collection(db, 'id')).id;

Queries
-------

    // get a doc
    const docSnap = await getDoc(doc(db, "pathname"));
    const data = docSnap.exists() ? { ...docSnap.data(), id: docSnap.id } : null;
    // get multiple docs
    const querySnap = await getDocs(query(collection(db, "pathname"), ...filters));
    for (const doc of querySnap.docs) {
     const data = doc.exists() ? { ...doc.data(), id: doc.id } : null;
     ...
    }
    // get collection Group multiple docs
    const querySnap = await getDocs(query(collectionGroup(db, "pathname"), ...filters);
    for (const doc of querySnap.docs) {
     const data = doc.exists() ? { ...doc.data(), id: doc.id } : null;
     ...
    }
    // filters
    where(field, comparison, value)
    orderBy(field, "desc|asc")
    limit(1)
    // cursors using field or docSnap
    startAt()
    startAFter()
    endAt()
    endBefore()
    // comparisons
    "<", "<=", "==", ">", ">=", "!="
    // array comparisons
    "array-contains", "array-contains-any", "in", "not-in"

Realtime Queries
----------------

    // get a doc
    const unsub = onSnapshot(doc(db, "pathname"), doc => {
     const data = doc.exists() ? { ...doc.data(), id: doc.id } : null;
     ...
    });
    // get multiple docs (query is optional)
    const unsub = onSnapshot(query(collection(db, "pathname"), ...filters), querySnap => {
     for (const doc of querySnap.docs) {
     const data = doc.exists() ? { ...doc.data(), id: doc.id } : null;
     ...
     }
     ...
    });
    

Batches and Transactions
------------------------

    // execute a transaction
    const txData = await runTransaction(db, async (transaction) => {
     const docRef = doc(db, "pathname");
     const docSnap = await transaction.get(docRef);
     const data = docSnap.exists() ? { ...doc.data(), id: doc.id } : null;
     const new_data = { ... };
     // await not necessary due to tx
     transaction.update(docRef, new_data);
     // return new data
     return { ... };
    });
    // batch writes
    const batch = writeBatch(db);
    const docRef = doc(db, "pathname");
    const docRef2 = doc(db, "pathname2");
    const docRef3 = doc(db, "pathname3");
    batch.set(docRef, { ... });
    batch.update(docRef2, { ... });
    batch.delete(docRef3);
    await batch.commit();

Note
----

All the above methods should be used within try / catch blocks for error checking. All of the `unsub` methods should be called within your framework's `onDestroy` methods to prevent memory leaks.

RXFire / Angular Fire
---------------------

    // get a doc
    const unsub = docData(doc(db, "pathname"), { idField: 'id' })
     .subscribe(doc => {
    });
    // get multiple docs
    const unsub = collectionData(query(collection(db, "pathname"), ...filters), { idField: 'id'})
     .subscribe(docs => {
    });
    // get a doc snap
    const unsub = docSnapshots(doc(db, "pathname"), { idField: 'id' })
     .subscribe(doc => {
    });
    // get a collection snap
    const unsub = collectionChanges(query(collection(db, "pathname"), ...filters), { idField: 'id'})
     .subscribe(docs => {
    });

J