We keep the likes in an array. It is easy to count the elements there and find out how many times a post is liked. We will make two small changes that will make this possible. The first one is in the API, which is the place where we prepare the post objects:

// backend/api/content.js
result.forEach(function(value, index, arr) {
  arr[index].id = ObjectId(value._id);
  arr[index].ownPost = user._id.toString() ===  ObjectId(arr[index].userId).toString();
  arr[index].numberOfLikes = arr[index].likes ?  arr[index].likes.length : 0;
  delete arr[index].userId;
  delete arr[index]._id;
});

A new numberOfLikes property is attached. The records did not have a likes property in the beginning. So, we have to check whether it exists before we use it. If we have numberOfLikes variable, we can update the label of the Like button in the frontend to the following code:

<input type="button" value="Like ({{posts[index].numberOfLikes}})" on-click="like:{{posts[index].id}}" /&gt...