How can I query an Array for a subdocument with mongoose? - node.js

Question

I am looking to query a subdocument that contains an array.
You can think of this as an application similar to medium.com or tumblr.com:
I have a user schema, and User's have many Posts. My post schema has a 'tags' key which is an array I am trying to create a route which will display all posts that have a certain tag.
So for instance,
GET /user/posts/:tag
GET /user/posts/dogs
might return back the data for all posts (by any user) that have the tag 'dogs'
{
description: 'dogs are cool',
title: 'huskies',
tags: ['dogs','animals','outdoors'],
original_poster: '34255352426'
},{
description: 'My puppies are nice',
title: 'Puppies',
tags: ['pugs','dogs','small'],
original_poster: '44388342426'
},{
description: 'I like cats more than dogs',
title: 'Cats',
tags: ['kittens','cats','dogs'],
original_poster: '15708213454'
}
Here is my User Schema:
const mongoose = require('mongoose'),
Schema = mongoose.Schema,
PostSchema = require('./post-model.js');
let UserSchema = new Schema({
email: {
type: String,
required: true,
unique: true
},
username: {
type: String,
required: true,
unique: true
},
password: {
type: String,
required: false, //only required for local users
unique: false,
default: null
},
following: {
type: [Number],
required: false,
unique: false
},
followers: {
type: [Number],
required: false,
unique: false
},
posts: [PostSchema],
})
module.exports = mongoose.model('User',UserSchema);
Here is my Post Schema:
const mongoose = require('mongoose'),
Schema = mongoose.Schema;
let PostSchema = new Schema({
description: {
type: String,
required: false,
unique: false
},
title: {
type: String,
required: false,
unique: false
},
tags: {
type: [String],
required: true
},
original_poster: {
type: String,
required: true
}
});
module.exports = PostSchema;
EDIT:
to clarify my question, imagine that this was a regular js object, here is what a function to return all data relevant to a specific tag:
let users = [];
let user1 = {
username: 'bob',
posts: [
{
title: 'dogs r cool',
tags: ['cats','dogs']
},
{
title: 'twd is cool',
tags: ['amc','twd']
}]
};
let user2 = {
username: 'joe',
posts: [{
title: 'mongodb is a database system that can be used with node.js',
tags: ['programming','code']
},
{
title: 'twd is a nice show',
tags: ['zombies','horror-tv','amc']
},
{
title: 'huskies are my favorite dogs',
tags: ['huskies','dogs']
}]
}
users.push(user1);
users.push(user2);
function returnPostByTag(tag) {
let returnedPosts = [];
users.forEach((user,i) => {
user.posts.forEach((post) => {
if(post.tags.includes(tag)) {
let includespost = {}
includespost.title = post.title;
includespost.tags = post.tags;
includespost.original_poster = user.username;
returnedPosts.push(includespost);
}
})
})
return returnedPosts;
}
If you want to see a full repl where I use a plain js example here it is: https://repl.it/repls/LavenderHugeFireant

Answer 1

You can do the following using Mongoose to return all users where the tags array in any of the subdocuments in the posts array includes tag:
User.find({ 'posts.tags': tag }, function(err, users) {
if (err) {
// Handle error
}
let filteredPosts = users
.map(user => {
user.posts.forEach(post => post.original_poster = user.username)
return user
})
.map(user => user.posts)
.reduce((acc, cur) => acc.concat(cur), [])
.filter(post => post.tags.includes(tag))
// Do something with filteredPosts
// ...such as sending in your route response
})
...where User is your Mongoose model and tag contains the tag string you want to query (perhaps from your route request).
If you are using promises then you could do:
User.find({ 'posts.tags': tag })
.then(users => {
let filteredPosts = users
.map(user => {
user.posts.forEach(post => post.original_poster = user.username)
return user
})
.map(user => user.posts)
.reduce((acc, cur) => acc.concat(cur), [])
.filter(post => post.tags.includes(tag))
// Do something with filteredPosts
// ...such as sending in your route response
})
.catch(err => {
// Handle error
})