Calculate the number of elements in a given array within a specific document

Question

Calculate the number of elements in a given array within a specific document

I'm in the process of setting up a blog where each post consists of multiple paragraphs. My goal is to be able to count the number of paragraphs in a specific post. The structure of my "Blog" collection, which contains documents (posts), looks like this:

{ id : String
  title : String
  paragraphs : [ { position: Int, body: String } ] }

I'm looking for a function that will return an Integer value. Maybe something along the lines of:

var NumberParagraphs = Blog.find( {id: id} ).paragraphs.length

(of course, this code doesn't actually work!). Can you guide me on how to approach this issue? I've been researching online and getting confused between using .count(), $size, or .aggregate.

javascript mongodb meteor count

Answer 1

Answer №1

When using the .find() method, keep in mind that it does not return a single document. You can either iterate through the documents as an array:

Blog.find({ id: id }).fetch().forEach(function(doc) {
     var NumParagraphs = doc.paragraphs.length;
     // Perform necessary actions
})

Alternatively, you can use .findOne() to retrieve a single document:

var doc = Blog.findOne({ id: id });
var NumParagraphs = doc.paragraphs.length;

These concepts are applicable not only to Meteor but also to raw MongoDB methods.

Answer 2

When using the .find() method, keep in mind that it does not return a single document. You can either iterate through the documents as an array:

Blog.find({ id: id }).fetch().forEach(function(doc) {
     var NumParagraphs = doc.paragraphs.length;
     // Perform necessary actions
})

Alternatively, you can use .findOne() to retrieve a single document:

var doc = Blog.findOne({ id: id });
var NumParagraphs = doc.paragraphs.length;

These concepts are applicable not only to Meteor but also to raw MongoDB methods.

Answer 3

Answer №2

Here's a demonstration of how to utilize the aggregate function alongside $size for your reference:

let totalWords = Article.aggregate([
    {
        $match : {
            "_id" : id
        }
    },
    {
        $project : {
            "wordCount" : {$size : '$words'}
        }
    }
]).wordCount;

Answer 4

Here's a demonstration of how to utilize the aggregate function alongside $size for your reference:

let totalWords = Article.aggregate([
    {
        $match : {
            "_id" : id
        }
    },
    {
        $project : {
            "wordCount" : {$size : '$words'}
        }
    }
]).wordCount;

Answer 5

Answer №3

It is recommended to

Access the length of paragraphs in a specific Blog document by using Blog.findOne({_id:id}).paragraphs.length

Appreciate your help

Answer 6

It is recommended to

Access the length of paragraphs in a specific Blog document by using Blog.findOne({_id:id}).paragraphs.length

Appreciate your help

Calculate the number of elements in a given array within a specific document

Answer №1

Answer №2

Answer №3

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