Firebase undefined error when array is empty

Question

Hi so I have this function that counts how many time a name appears in a list:

fire.firestore()
.collection("eventLikes")
.doc(eventID)
.onSnapshot((docSnapshot) => {
      
      //}
    // if(docSnapshot.data().ActivityLikes.length === 0) {
        const nameCounts = docSnapshot.data().ActivityLikes.reduce((acc, cur) => {
            acc[cur.name] = (acc[cur.name] || 0) + 1;
        return acc;
}, {});

docSnapshot.data() is empty at the start and docSnapshot.data().ActivityLikes.length is sometimes empty so [] in firebase. But in NextJs i keep gettin this error:

How should i go about fixing this error?

Dharmaraj · Accepted Answer · 2022-04-16 18:05:22Z

1

If the document doesn't exist then .data() returns undefined. You should if that exists first:

if (docSnapshot.exists) {
  // process data
} else {
  console.log("Document does not exists")
}

answered Apr 16, 2022 at 18:05

Dharmaraj

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