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mongodb not detecting unique value in my node js project

I'm working on mongodb with node js and I realized that even though I used the unique true property on unique fields in my project, I realized that it doesn't work, what is the reason?
my code is like this
const CourseSchema = new Schema({
name: {
type: String,
required : true,
unique:true
},
description: {
type: String,
required: true,
trim: true,
},
createdAt: {
type: Date,
default: Date.now,
},
});
i want to prevent this code from saving duplicate usernames.

Such a check if not directly possible with the mongoDB library. However it is supported out of the box if you use mongoosejs

It may be possible that you already have duplicate values in your document before defining this property Delete the messed data from the MongoDB collections,
or make sure that mongodb auto indexing is true
mongoose.connect('url', {
useNewUrlParser: true,
useCreateIndex: true,
autoIndex: true,
})

I tried many ways, but I realized that this problem is version-related.
I found the solution by updating the version, thank you for your solution support.

is there a way to create Keystone lists in runtime after keystone initialisation?

I'd like to create a KeystoneJs (v5.0.6) during runtime as some lists might be dynamically generated by the user.
If I run the following command after keystone has been intialised, I get the error: "Error: keystone.createList must be called before keystone.prepare()"
keystone.createList("MyDynamicList", {
fields: {
name: { type: Text },
email: {
type: Text,
isUnique: true,
},
},
});
Is there a way lists can be generated dynamically during runtime?

this is not possible, all the lists (and fields) has to be provided in keystone.createList method. keystone generates all the schema for GraphQL before you run keystone.connect.
There was a PR and request for delaying initialization in case someone wanted to add a field using a plugin before keystone.connect call which was denied.
Based on that discussion it is highly unlikely that this type of request even be priority for long.

How to make strict associations in Sails.js

Here are my two models that were generated using sails generate api model_name
Guitar.js
module.exports = {
schema: true,
attributes: {
brand:{
type: 'string',
required: true
},
messages:{
collection: 'message',
via: 'guitar'
}
}
};
Message.js
module.exports = {
schema: true,
attributes: {
text:{
type: 'string',
required: true
},
author:{
type: 'string',
defaultsTo: 'Anonymous author'
},
guitar:{
model: 'guitar',
required: true
}
}
};
Basically, a guitar can have many messages.
The problem comes when I insert new messages into the DB:
POST http://localhost:1337/message/
With JSON content:
{
"text": 4,
"author": "33434",
"guitar": null,
"extra": "This attribute will be removed because schema: true"
}
If I send this, the server will throw an error because the message must have a guitar.
However, if I instead write "guitar": 34, and 34 is a guitar ID that doesn't exist, the message will be added, and guitar will be changed to null. Weird.
This seems to be a bug, or maybe it's the intended behaviour but with a NoSQL database in mind.
I need to make strict associations so that all data makes sense. I hope I don't have to create my own controller manually that handles this logic the way I want.
Basically what I want is that Sails throws an error when the ID of the association doesn't exist.
By the time I write this, I came up with a solution: Just configure this on the DB server (MySQL, etc) so that the foreign key must exist and then handle the error in Sails. But I'm not very happy with it since it depends on the DB server. I'd like this to work even with localDiskDb.
My other solution would be to actually write manually a controller and see what happens by using something like Guitar.find(id).add(new_message) (maybe it's wrong, I haven't tested this)

I am not sure about this but have you tried like this :
http://localhost:1337/message/create?text=4&author=3343&guitar=somerandomString

How do I create an A record in a hosted zone with the AWS node SDK

I am using the Route 53 Node API to create and configure a hosted zone. Creating the zone works fine, but when I try to use the changeResourceRecordSets function to add an A record, I get an error that says 'InvalidInput: Invalid request' but doesn't say what is invalid about it. Here is my request params object:
var zoneConfig = {
ChangeBatch: {
Changes: [{
Action: 'CREATE',
ResourceRecordSet: {
Name: 'my.domain.com',
Type: 'A',
Region: 'us-east-1',
TTL: 300,
ResourceRecords: [{
Value: '111.222.111.000'
}]
}
}],
Comment: 'direct hosted zone A record to point to the server'
},
HostedZoneId: 'ZZH1GLJKE22DK'
};
rt53.changeResourceRecordSets( zoneConfig, function(...
Any ideas what might be wrong in the request?

Finally figured it out. The problem was the Region field in the ResourceRecordSet. I missed it in the documentation, but that is only to be used for latency-based resource record sets. So, deleting that line fixed the issue
Really wish the API error message could have just said that.

Create multiple user contracts in Meteor

I want to create a system where multiple contracts can be created belonging to different users.
In Django, Ruby, etc., I would create a model Contract with field user = models.ForeignKey(settings.AUTH_USER_MODEL) but I don't know how to do this in Meteor.
Is it better to make a schema with
Schema.User = new SimpleSchema({
contracts: {
type: [Object],
},
"contracts.$.start_date": {
type: Date,
},
"contracts.$.end_date": {
type: Date,
},
"contracts.$.salary": {
type: Number,
}
});
or something like that? And then use meteor-autoform to create these? It seems very difficult to make objects relational in Meteor.

MongoDB isn't a relational database and so you'll need to manually handle relationships yourself (using multiple queries). Traditionally a Mongo document would use embedding whenever possible and use separate collections when necessary. See here for more information:
MongoDB relationships: embed or reference?
However, Meteor throws a spanner in the works since the publish model can only publish top-level documents, and there's little support for document hierarchies when writing templates etc.
Therefore the normal approach under Meteor is to create table for each collection and to have a records refer to other records using an ID:
Schema.User = new SimpleSchema({
contracts: {
type: [String],
},
...
});
Schema.Contract = new SimpleSchema({
user: {
type: String,
index: true
},
...
});
Although this will result in you having to do multiple queries, the structure will work very will with Meteor's design philosophies.