Comparing mongoose _id and strings - node.js

I have a node.js application that pulls some data and sticks it into an object, like this:
var results = new Object();
User.findOne(query, function(err, u) {
results.userId = u._id;
}
When I do an if/then based on that stored ID, the comparison is never true:
if (results.userId == AnotherMongoDocument._id) {
console.log('This is never true');
}
When I do a console.log of the two id's, they match exactly:
User id: 4fc67871349bb7bf6a000002 AnotherMongoDocument id: 4fc67871349bb7bf6a000002
I am assuming this is some kind of datatype problem, but I'm not sure how to convert results.userId to a datatype that will result in the above comparison being true and my outsourced brain (aka Google) has been unable to help.

Mongoose uses the mongodb-native driver, which uses the custom ObjectID type. You can compare ObjectIDs with the .equals() method. With your example, results.userId.equals(AnotherMongoDocument._id). The ObjectID type also has a toString() method, if you wish to store a stringified version of the ObjectID in JSON format, or a cookie.
If you use ObjectID = require("mongodb").ObjectID (requires the mongodb-native library) you can check if results.userId is a valid identifier with results.userId instanceof ObjectID.
Etc.

ObjectIDs are objects so if you just compare them with == you're comparing their references. If you want to compare their values you need to use the ObjectID.equals method:
if (results.userId.equals(AnotherMongoDocument._id)) {
...
}

converting object id to string(using toString() method) will do the job.

The three possible solutions suggested here have different use cases.
Use .equals when comparing ObjectId on two mongoDocuments like this
results.userId.equals(AnotherMongoDocument._id)
Use .toString() when comparing a string representation of ObjectId to an ObjectId of a mongoDocument. like this
results.userId === AnotherMongoDocument._id.toString()

According to the above,i found three ways to solve the problem.
AnotherMongoDocument._id.toString()
JSON.stringify(AnotherMongoDocument._id)
results.userId.equals(AnotherMongoDocument._id)

The accepted answers really limit what you can do with your code. For example, you would not be able to search an array of Object Ids by using the equals method. Instead, it would make more sense to always cast to string and compare the keys.
Here's an example answer in case if you need to use indexOf() to check within an array of references for a specific id. assume query is a query you are executing, assume someModel is a mongo model for the id you are looking for, and finally assume results.idList is the field you are looking for your object id in.
query.exec(function(err,results){
var array = results.idList.map(function(v){ return v.toString(); });
var exists = array.indexOf(someModel._id.toString()) >= 0;
console.log(exists);
});

I faced exactly the same problem and i simply resolved the issue with the help of JSON.stringify() as follow:-
if (JSON.stringify(results.userId) === JSON.stringify(AnotherMongoDocument._id)) {
console.log('This is never true');
}

Mongoose from 5 to 6 migration guide:
"Mongoose now adds a valueOf() function to ObjectIds. This means you can now use == to compare an ObjectId against a string."
https://mongoosejs.com/docs/migrating_to_6.html#objectid-valueof

Here is an example that explains the issue and why it confusing for many. Only the first console log shows the object in its true form, and any other debuging/loging will be confusing because they look the same.
// Constructor for an object that has 'val' and some other stuffs
// related to to librery...
function ID(_val) {
this.val = _val;
this.otherStuff = "other stuffs goes here";
}
// function to help user get usefull infos from the Object
ID.prototype.toString = function toString() {
return `${this.val}`;
};
// Create new Object of type ID
const id = new ID('1234567');
console.log("my ID: ", id); // my ID: Object {
// val: "1234567",
// otherStuff: "other stuffs goes here"
// }
console.log("my ID: " + id); // my ID: 1234567
console.log(id === '1234567'); // false
console.log(id == '1234567'); // true
console.log(id.toString() === '1234567'); //true
console.log(`${id}` === '1234567'); // true
console.log(new ID('1234567') === id); // false

Related

an undefined variable in node.js with the mongoose query

let customer_count;
let cust_string;
Customer.count({}, function(err, count){ customer_count = count+1; cust_string = 'cust' + customer_count });
// Create a customer object with escaped and trimmed data.
var customer = new Customer(
{ customerId: cust_string})
I would like to make a self-defined customer id for my model's index. I want that id looks like 'cust0001' something and the next one will be 'cust0002'. So, I used the count() from mongoose to join the string but unforunately, when I am creating the customer object, the 'cust_string' is said to be undefined. Could you please help me fix it?
Callback doesn't return anything. You have to create customer inside the same function you're calculating cust_string. Other option is to use promises/async/await etc.
Your code will work this way:
let customer_count;
let cust_string;
Customer.count({}, function (err, count) {
// calculate id
customer_count = count + 1;
cust_string = 'cust' + customer_count;
// Create a customer object
var customer = new Customer({ customerId: cust_string });
});
But this is not a good way to implement auto-increment in mongodb. It will be very expensive operation.
I recommend you to use mongoose-auto-increment. It saves sequences in database and prevents duplicate keys.

Taking a variable out of object node js

I'm using this to get player's status in steam. I'm kinda new to Node.JS so that's why I'm kind of confused.
s.getPlayerSummaries({
steamids: ['76561198152643711'],
callback: function(err, data) {
var myData = data["response"]["players"];
}
});
which returns me
[ { steamid: '34264356456',
gameextrainfo: 'Counter-Strike: Global Offensive',
gameid: '730' } ]
I tried using myData["gameid"] but that didn't work either.
I also used json.stringify but when I do json.stringify(myData) and then take out gameid it returns me undefined. All I'm trying to do is take out these 3 veriables out of that object or array, idk tbh.
You're receiving an array of objects but try to handle it as an object directly. Also you should use JSON.parse(data) if data is a string.
var parsedArray = JSON.parse(data); // step not needed if data is already an object/array
Once done you got that you need to retrieve your object that is the first element of your array.
var myObject = parsedArray[0]; // data[0] if data was not a string
Eventually to retrieve your object's gameid property you can do this:
var myGameId = myObject.gameid
Hope it helps.
It seems like myData is an array of objects. So to read the first gameId in the array do
var firstGameId = myData[0].gameid;

Mongoose: disable empty query returning a document

When using Mongoose (with bluebird in my case, but using callbacks to illustrate), the following codes all return a document from the collection:
model.findOne({}, function(err, document) {
//returns a document
})
model.findOne(null, function(err, document) {
//returns a document
})
model.findOne([], function(err, document) {
//returns a document
})
I would like to know if and how I can disable this kind of behaviour, as it is becoming a liability to my code where I infer queries from data a user feeds into the system. Especially the null query returning a valid document worries me.
As of right now I check the input for being an non-empty, non-array, non-null object, but it's becoming a bit cumbersome at scale.
What would be the best way to exclude this behaviour?
Not sure if it is the best way to go about it, but right now I've settled on using a pre-hook on the model itself which checks for the _conditions property of the 'this' object (which I inferred from printing seems to hold the query object) to not be empty.
Inserting a self-defined object in the next functionality causes the Promise to reject in which the query was originally called from.
( _ is the underscore package)
//model.js
//model is a mongoose.Schema type in the following code
model.pre('findOne', function(next) {
var self = this
if (_.isEmpty(self._conditions)) {
next(mainErrors.malformedRequest)
} else {
next()
}
})

Mongoose.js conditional populate

I'm working with some old data where some of the schema has a "mixed" type.
Basically sometimes a value will be a referenced ObjectID, but other times it'll be some text (super poor design).
I unable to correctly populate this data because of the times a non-ObjectID appears.
So, for my actual question: Is it possible to create a populate (on a collection) that is conditional; I need to be able to tell the populate to skip those other values.
Yes, you can do that check the middleware function on the Mongoose API reference
http://mongoosejs.com/docs/middleware.html
What you need to do is before you populate those data, you validate the data if is is Object ID or not, if it is Object ID, you call next() to pass the next function, else you just return, this will skip it
Example
xSchema.pre('validate', function(next){
var x = this;
var checkXType = typeof x.id;
if (checkXType === String) {
return;
} else {
next();
}
});

Mongoose: what's up with "_doc"?

It seems Mongoose is doing something really funky internally.
var Foo = new mongoose.model('Foo', new mongoose.Schema({a: String, b: Number}));
var foo = new Foo({a: 'test'; b: 42});
var obj = {c: 1};
foo.goo = obj; // simple object assignment. obj should be
// passed by reference to foo.goo. recall goo
// is not defined in the Foo model schema
console.log(foo.goo === obj); // comparison directly after the assignment
// => false, doesn't behave like normal JS object
Essentially, any time you try to deal with properties of a Mongoose model that aren't
a) defined in the model's schema or
b) defined as the same type (array, obj, ..) ... the model doesn't even behave like a normal Javascript object.
Switching line 4 to foo._doc.goo = obj makes the console output true.
edit: trying to reproduce weirdness
example 1:
// Customer has a property 'name', but no property 'text'
// I do this because I need to transform my data slightly before sending it
// to client.
models.Customer.find({}, function(err, data) {
for (var i=0, len=data.length; i<len; ++i) {
data[i] = data[i]._doc; // if I don't do this, returned data
// has no 'text' property
data[i].text = data[i].name;
}
res.json({success: err, response:data});
});
_doc exist on the mongoose object.
Because mongooseModel.findOne returns the model itself, the model has structure (protected fields).
When you try to print the object with console.log it gives you only the data from the database, because console.log will print the object public fields.
If you try something like JSON.stringify then you get to see inside the mongoose model object. (_doc, state ...)
In the case where you want to add more fields in the object and it's not working
const car = model.findOne({_id:'1'})
car.someNewProp = true // this will not work
If later you set the property to the object car and you didn't specify in the Model Schema before then Mongoose model is validating if this field exists and if it's the valid type.
If the validation fails then the property will not be set.
Update
Maybe I misunderstood your original question, but now it looks like the nature of your question changed, so the below information isn't relevant, but I'm leaving it. :)
I tested your code and it works fine for me. Mongoose doesn't execute any special code when you set properties that aren't part of the schema (or a few other special properties). JavaScript currently doesn't support calling code for properties that don't yet exist (so Mongoose can't get in the way of the set of the goo property for example).
So, when you set the property:
foo.goo = { c: 1 };
Mongoose isn't involved. If your console.log was something other than the code you displayed, I could see that it might report incorrectly.
Additionally, when you send the results back as JSON, JSON.stringify is being called, which calls toString on your Mongoose Model. When that happens, Mongoose only uses the properties defined on the schema. So, no additional properties are being sent back by default. You've changed the nature of the data array though to directly point at the Mongoose data, so it avoids that problem.
Details about normal behavior
When you set the property goo using Mongoose, quite a few things happen. Mongoose creates property getters/setters via the Object.defineProperty (some docs). So, when you set the goo property, which you've defined as a [String], a few things happen:
Mongoose code is called prior to the value being set onto the object instance (unlike a simple JavaScript object)
Mongoose creates an array (optionally) to store the data (a MongooseArray) which will contain the array data. In the example you provided, since you didn't pass an array, it will be created.
Mongoose will attempt to cast your data to the right type
It will call toString on the data passed as part of the cast.
So, the results are that the document now contains an array with a toString version of the object you passed.
If you checked the contents of the goo property, you'd see that it's now an array with a single element, which is a string that contains [object Object]. If you'd picked a more basic type or matched the destination property storage type, you would see that a basic equality check would have worked.
you can use toJSON() instead of _doc
Try using lean
By default, Mongoose queries return an instance of the Mongoose Document class. Documents are much heavier than vanilla JavaScript objects, because they have a lot of internal state for change tracking. Enabling the lean option tells Mongoose to skip instantiating a full Mongoose document and just give you the POJO.
https://mongoosejs.com/docs/tutorials/lean.html
Had same problem. Instead of updating my model.
const car = model.findOne({_id:'1'})
let temp = JSON.stringify(car);
let objCar = JSON.parse(temp);
objCar.color = 'Red'; //now add any property you want
this solves my problem
I was stuck on this today... Drove me nuts. Not sure if the below is a good solution (and OP has mentioned it too), but this is how I overcame this issue.
My car object:
cars = [{"make" : "Toyota"}, {"make" : "Kia"}];
Action:
console.log("1. Cars before the color: " + car);
cars.forEach(function(car){
car.colour = "Black"; //color is NOT defined in the model.
});
console.log("2. Cars after the color: " + car);
Problematic console output:
1. Cars before the color: [{"make" : "Toyota"}, {"make" : "Kia"}];
2. Cars after the color: [{"make" : "Toyota"}, {"make" : "Kia"}]; //No change! No new colour properties :(
If you try to pass in this property that was undefined in the model, via doc (e.g. car._doc.color = "black"), it will work (this colour property will be assigned to each car), but you can't seem to access it via EJS (frontend) for some reason.
Solution:
(Again, not sure if this is the best way... but it worked for me): Add in this new property (colour) in the car model.
var carSchema = mongoose.Schema({
make: String,
color: String //New property.
})
With the model redefined, everything worked as normal / expected (no _doc 'hacks' needed etc.) and I lived another day; hope it helps someone else.
There is some weirdness with Mongoose models and you have to check that Mongoose doesn't already have a model created in it's models array.
Here is my solution:
import mongoose from 'mongoose';
createModel = (modelName="foo", schemaDef, schemaOptions = {})=> {
const { Schema } = mongoose;
const schema = Schema(schemaDef, schemaOptions);
const Model = mongoose.models[modelName] || mongoose.model(modelName, schema);
return Model;
}
I use my own mongoose model class and base class for my models. I made this and it should work for you.
For those using spread(...) and/ can't see a solution, here's an example of #entesar's answer
Instead of spread or ._doc in:
import User from "./models/user";
...
async function createUser(req, res) {
const user = await User.create(req.body);
res.status(201).json({
message: "user created",
data: {
...user // OR user._doc,
token: "xxxxxxxx",
},
});
}
...
Use this
import User from "./models/user";
...
async function createUser(req, res) {
const user = await User.create(req.body);
res.status(201).json({
message: "user created",
data: {
...user.toJSON(),
token: "xxxxxxxx",
},
});
}
...
Ps: took me a while to understand the answer.
You should add .lean() on the find to have it skip all the Model "magic".

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