Query Nested Object in Firebase Firestore

Question

I have in my Firestore database a list of documents that include this field 'Participants', as a nested object.

I want to make a query that gets only one document from the database (to see if it exists or not) that has (for example) user id 5 and 6.

This is what my code looks like

const chatsCollection =  db.collection('chats');

async function createChat(myId, otherUserId){

  chat = await chatsCollection
  .where(`participants.${myId}`, "==", true)
  .where(`participants.${otherUserId}`, "==", true)
  .limit(1).get();

  if(!chat.exists){
     alert('chat doesnt exist')
     //create chat
  } else {
     alert('chat exists')
     //do something else
  }

}

However, even if the chat with the participants object does indeed exist in the database, the result of the code indicates that it doesn't.

Here is the structure of the data when it is added to the database

    var chat_key = (Math.random() + 1).toString(36).substring(2);
    
    chatData = {
        key: chat_key,
        created_at: new Date(),
        participants: {
            myId: true,
            otherUserId: true,
        }
    }

    chatsCollection.doc(chat_key).set(chatData);

I appreciate any help on how to solve this problem. Thanks:)

Answer 1

on method collection, you can use empty property to see if the query getting data or not

if(chat.empty){
 alert('chat doesnt exist')
 //create chat
} else {
 alert('chat exists')
 //do something else
}

to get only one document from your query, you can use

chat.docs[0].data();