How can I get documents inside a subcollection in every document in Firebase Firestore?

Question

How can I get all the documents inside the subcollection "userPosts" in Firebase Firestore with JavaScript? You can see my database structure in the pictures below.

Here is what I have tried:

firebase.auth().onAuthStateChanged(function(user) {

    var postRef = database.collection('posts').doc().collection('userPosts');

    postRef.get().then(snapshot => {
        setupPosts(snapshot.docs)
    })

    const posts = document.querySelector('.posts');

    const setupPosts = (data) => {

        let html = '';
        data.forEach(doc => {
            const post = doc.data();

            console.log(post)

            const li = `
            <li>
                <div class="title">${post.title}</div>
                <div class="content">${post.content}</div>
            </li>
            `;
            html += li
        })

        posts.innerHTML = html;

    }
})

What this code should do is to get the documents in the subcollection "userPosts". And it should go into every document in the collection "posts" and then go into "userPosts" and get every document in that subcollection.

First collection "posts"

Subcollection "userPosts"

I'm not sure I understand. Can you show what you tried already, or why the code from this documentation doesn't work for you? firebase.google.com/docs/firestore/query-data/… — Frank van Puffelen

Doug Stevenson Doug Stevenson · Accepted Answer · 2020-10-08T16:07:27

It sounds like you want a collection group query. This will give you all the documents in all subcollections named "userPosts":

const query = database.collectionGroup("userPosts")
query.get().then(querySnapshot => { ... })

How can I get documents inside a subcollection in every document in Firebase Firestore?

2 Answers