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How to use mongo db regex in express

I want to use regex such that in the url /todos?q=dho gives me all the results regarding to dho.
I tried using $regex syntax in the query.find() method but not giving the desired results. Thank You in advance
How and where to use regex for mongo db search such that I get the results?
todoRouter.get("/", async (req, res) =\> {
let query = req.query;
try {
const todos = await todoModel.find(query);
res.send(todos);
} catch (err) {
res.send(err);
}
})

If the name of the column you are searching in is name, code would look like this
const todos = await todoModel.find({"name": /.*{{your_query_param}}.*/});

How can use the .count() method in mongoose to count multiple collections

I have a operation that counts all of the registered users which there is a collection named registered-users in my MongoDB.
Here is how I accomplished that:
const User = require("../models/User")
const Topic = require("../models/Topic")
router.get('/', async (req, res) => {
await User.count((err, registeredUsers) => {
if (err){
console.log(err)
} else {
res.render("register", {registeredUsers})// using EJS for my template engine
}
})
})
so this let's me count the total users registered but I have another collection in the db named topics that I would like to get a total count of as well. how can I do that without having to res.render again (I'm not even sure if that works or not) and pass in another object? Is this possible to count the users and the topics (which is a different collection and model)?
The goal is that in the ejs it has something that says :
Total Users signed up: registeredUsers
Total Topics created: totalTopics

Model.count()
Counts number of documents that match filter in a database collection.
This method is deprecated. If you want to count the number of documents in a collection, e.g. count({}), use the estimatedDocumentCount() function instead. Otherwise, use the countDocuments() function instead.
source: https://mongoosejs.com/docs/api.html#model_Model-count
Also, since you are using async function, we can use Promise.all() to run queries in parallel.
const User = require("../models/User")
const Topic = require("../models/Topic")
router.get('/', async (req, res) => {
const [userCount, topicCount] = await Promise.all([
User.countDocuments({}),
Topic.countDocuments({})
])
// using EJS for my template engine
res.render("register", {
registeredUsers: userCount,
totalTopics: topicCount
})
})

Error while deleting a value of element in mongoDB array using filter function?

I tried to find the solutions over here but unable to get success while using $pull as the array values I have does not contain `mongo_id'.
So the scenario is that , I am trying to delete the specific comment of the particular user which I am passing through query params. M
My mongo data looks like this:
Now I am making API Delete request like this : http://localhost:8000/api/articles/learn-react/delete-comment?q=1 on my localhost .
ANd finally my code looks like this:
import express from "express";
import bodyParser from "body-parser";
import { MongoClient } from "MongoDB";
const withDB = async (operations, res) => {
try {
const client = await MongoClient.connect(
"mongodb://localhost:27017",
{ useNewUrlParser: true },
{ useUnifiedTopology: true }
);
const db = client.db("my-blog");
await operations(db);
client.close();
} catch (error) {
res.status(500).json({ message: "Error connecting to db", error });
}
};
app.delete("/api/articles/:name/delete-comment", (req, res) => {
const articleName = req.params.name;
const commentIndex = req.query.q;
withDB(async(db) => {
try{
const articleInfo = await db.collection('articles').findOne({name:articleName});
let articleAllComment = articleInfo.comments;
console.log("before =",articleAllComment)
const commentToBeDeleted = articleInfo.comments[commentIndex];
//console.log(commentToBeDeleted)
// articleAllComment.update({
// $pull: { 'comments':{username: commentToBeDeleted.username }}
// });
articleAllComment = articleAllComment.filter( (item) => item != commentToBeDeleted );
await articleAllComment.save();
console.log("after - ",articleAllComment);
//yaha per index chahiye per kaise milega pta nhi?
//articleInfo.comments = gives artcle comment
res.status(200).send(articleAllComment);
}
catch(err)
{
res.status(500).send("Error occurred")
}
},res);
});
I have used the filter function but it is not showing any error in terminal but also getting 500 status at postman.
Unable to figure out the error?

I believe you'll find a good answer here:
https://stackoverflow.com/a/4588909/9951599
Something to consider...
You can use MongoDB's built-in projection methods to simplify your code.
https://docs.mongodb.com/manual/reference/operator/projection/positional/#mongodb-projection-proj.-
By assigning a "unique ID" to each of your comments, you can find/modify the comment quickly using an update command instead of pulling out the comment by order in the array. This is more efficient, and much simpler. Plus, multiple read/writes at once won't interfere with this logic during busy times, ensuring that you're always deleting the right comment.
Solution #1: The recommended way, with atomic operators
Here is how you can let MongoDB pull it for you if you give each of your comments an ID.
await db.collection('articles').updateOne({ name:articleName },
{
$pull:{ "comments.id":commentID }
});
// Or
await db.collection('articles').updateOne({ name:articleName, "comments.id":commentID },
{
$unset:{ "comments.$":0 }
});
Solution #2 - Not recommended
Alternatively, you could remove it by index:
// I'm using "3" here staticly, put the index of your comment there instead.
db.collection('articles').updateOne({ name:articleName }, {
$unset : { "comments.3":0 }
})
I do not know why your filter is erroring, but I would recommend bypassing the filter altogether and try to utilize MongoDB's atomic system for you.

How to return value of both of the consecutive async functions in JS?

I've recently started with web development, and am a novice in JavaScript.
I'm currently working on a Blog Project and using Firebase as the backend, and Firestore as the Database.
PROJECT-
using the following project structure
Firestore DB ->
-Posts
-post1
-post2
-post3
...
-authors
-author1
-author2
..
-subscribers
...
I'm using this function to retrieve my posts from Firestore.
app.get('/:id', (req, res) => {
const id = req.params.id;
async function getDocument(id) {
const doc = await db.collection('Posts').doc(id).get();
if (!doc.exists) {
console.log('No such document!');
} else {
return doc.data();
}
}
getDocument(id).then(function (data) {
res.render('post',{ articleInfo:data} );
// that send back an object containing post details
})
Now, from the JSON I get from the above function, I want to use the value of "Author" to get the author's details from the another collection(run another async function),
and then send this data along with the data from previous function(used to get post details) together in res.render()
For example
I make a get request for a post and get back it's details. Inside which get the author's name "{..,"author : mike-ross",..} " .
Now, after .then, I use this value to run another async function get this author's JSON from the Authors collection. and pass the result from both the functions together in res.render() to get diplayed on the page.

You could have one async function that does both calls and returns an object with both results:
async function getDocWithDetails (id) {
const doc = await getDocument(id);
const authorInfo = await getAuthorInfo(doc.author);
return {
doc: doc.data(),
authorInfo: doc.data()
}
}
getDocWithDetails(id).then((data) => {
res.render('post', data) // has data.doc and data.authorInfo
});

Just go for it, same way you did the first half :-)
In general (at least at my work projects), it's good practice to setup multiple getters for each collection or one main getter where the collection is a secondary argument.
Here's the second variant with dynamic variant (but the first one is just as valid). Especially if you're not using typescript or flowtype to typecheck what you're passing, then it's more prone to unexpected errors by passing incorrect param, I'm just lazy to write the similar function in the answer twice.
const getDocumentById = async (id, collection) => {
const doc = await db.collection(collection).doc(id).get()
if (!doc.exists) {
throw Error(`Doc with id "${id}" doesn't exist on collection "${collection}"`)
}
return doc.data()
}
Now that we have our generic getter setup, you just need to create a function that fetches both.
As a precursor, I have taken some creative liberties with the answer, since the question is missing some cruicial info about documents.
At the very least (and if you don't you should, it's good firebase practice) I presume you have a link to the authorId inside Posts document.
Posts
-> post
-> id
-> authorId
-> some_other_fields
Authors
-> author
-> id
-> some_other_fields
With the following structure in mind, your answer will look something like this:
const getAuthorByPostId = async (id) => {
try {
const post = await getDocumentById(id, 'Posts')
const { authorId } = post
const author = await getDocumentById(authorId, 'Authors')
// I'm not sure how your res is structured, but could look something like this
res.render('page', { articleInfo: post, authorInfo: author })
} catch (error) {
console.error(error.message)
}
// in case it was unable to fetch data
return null
}

Post Multiple Objects Inside Express Route

I would like to post multiple objects to my mongo database inside of an express route. Currently, everything is working fine when I do it as a single object (ie ONE casino), please see below, but instead of doing this a million times over, can someone help me do it as one giant data dump so I can post ALL my casinos?
Here is my route that works fine for posting a single object:
router.post('/post', async (req, res) => {
console.log(req.body);
const casinoD = new Casino({
casino: req.body.casino,
table_and_other: req.body.table_and_other,
poker: req.body.poker,
slot_machines: req.body.slot_machines,
total_gaming_win: req.body.total_gaming_win,
year: req.body.year,
month: req.body.month,
combined_date: req.body.combined_date
})
try {
const newCasino = await casinoD.save()
res.status(201).json(newCasino)
} catch (err) {
res.status(400).json({ message: err.message})
}
})
I also understand mongoimport is a better way to do this - however that had its own issues in of itself.
Thanks

Like #JDunken said, you can iterate over the POST body as an array and insert in bulk. You'll want to use
insertMany for speed. To insert millions of records, you will probably want to put a sane limit on the number of records per request, and send API requests in batches. Validation is optional, as Mongoose will run validation according to the schema. It depends on how you want to handle validation errors. Make sure to read up on the ordered and rawResult options for that as well.
router.post('/post', async (req, res) => {
// you should sanity check that req.body is an array first, depending on how robust you want error handling to be
const casinos = req.body.filter(input => isValid(input));
try {
const insertedCasinos = await CasinoModel.insertMany(casinos, { ordered: false });
res.status(201).json(insertedCasinos)
} catch (err) {
res.status(400).json({ message: err.message})
}
})
const isValid(input) {
let valid = true;
// implement input validation
return valid;
}