MongoDB Aggregation ..对数组进行计数会在javascript上产生输出。 使用nodeJS，猫鼬

Question

this is my mongoose schema

    var testSchema = new mongoose.Schema({
    name: String,
    image: String,
    comments: [
        {
        type: mongoose.Schema.Types.ObjectId,
        ref: "Comment"
        }
    ]
});

so every user has a name, picture and comments. the comments are array. basically i have 10 users, with different comments, i want to count how many comments on per user and display it on the html..

i have tried this

 db.users.aggregate({$project: { count: {$size:"$comments"}}})

it counts the comments per user of all user... how can i output this on the html? and how can i just perform this command on 1 user? not to all user... thanks!

Answer 1

For finding the number of comments made by a single user, use the following command in mongoose.

Users.findOne({_id: ObjectId("57cdf6b3fbccf41198389aca")}, function(err, user) {
     if(err) {
       //handle error
     } else if(!user) {
       //no user found
     } else {
       //user found
       if(user.comments) {
           console.log('user comments length', user.comments.length);
       } else {
           console.log('no user comments');
       }
     }
})