Firestore - 如何根据特定字段检查文档是否存在

Question

What I want to achieve is to check if a document exist based on a field like liker_id and if it exist then return and if not then create a new document with the liker_id.

I've tried both snapshot.exists and doc.exists but they seem to give weird behaviors where the console.log doesn't get triggered or collection still adds document even though it already exists.

const liker = db
  .collection("post")
  .doc('ubxL0nDCLHgrtEyQ5TEV')
  .collection("votes")
  .where("liker_id", "==", "user-TVe8mMRU47cnfO4xbl9yQEEE4XB3")
  .get()
  .then(snapshot => {
    snapshot.forEach(doc => {
      if (doc.exists) {
        console.log("exist");
      } else {
        console.log("not exist");
      }
    });
  })
  .catch(error => {
    console.log(error);
  });

Answer 1

Would you try the code like this?

const liker = db
  .collection("post")
  .doc('ubxL0nDCLHgrtEyQ5TEV')
  .collection("votes")
  .where("liker_id", "==", "user-TVe8mMRU47cnfO4xbl9yQEEE4XB3")
  .get()
  .then(snapshot => {
    const data = snapshot.val();
    data.forEach(doc => {
      if (doc.exists) {
        console.log("exist");
      } else {
        console.log("not exist");
      }
    });
  })
  .catch(error => {
    console.log(error);
  });