How do I get Realtime document updates from Firebase Firestore with change.type =="added'

I presently can realtime update modified data with the following code. What I am trying to accomplish is to listen for new documents added and then realtime update my posts. I believe it is in line 8 // listen for new docs that is causing the issues.

getPosts() {
  this.posts = [];

  let loading = this.loadingCtrl.create({
    content: "Loading Feed..."
  });

  loading.present();

  let query = firebase.firestore().collection("posts").orderBy("created", "desc").limit(this.pageSize);

  query.onSnapshot((snapshot) => {
    let changedDocs = snapshot.docChanges();

    changedDocs.forEach((change) => {

      if (change.type == "added") {
        console.log("New Message: ", change.doc.data());
        for (let i = 0; i < this.posts.length; i++) {
          // if (this.posts[i].id === change.doc.id) {
          if (change.doc.isEqual(this.posts[i])) {
            this.posts[i] = change.doc;
          }
        }
      }


      if (change.type == "modified") {
        console.log("Modified Message: ", change.doc.data());
        for (let i = 0; i < this.posts.length; i++) {
          if (this.posts[i].id == change.doc.id) {
            this.posts[i] = change.doc;
          }
        }
      }

    })
  })

query.get()
  .then((docs) => {

    docs.forEach((doc) => {
      this.posts.push(doc);
    })

    loading.dismiss();

    this.cursor = this.posts[this.posts.length - 1];

    console.log(this.posts);

  }).catch((err) => {
    console.log(err)
  })
}

from How do I get Realtime document updates from Firebase Firestore with change.type =="added'