Discussion on: How to create a simple and beautiful chat with MongoDB, Express, React and Node.js (MERN stack)

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In server/Message.js file:

const messageSchema = new mongoose.Schema({
content: String,
name: String,
}, {
timestamps: true, -----> this line
});

Is timestamp true by default?

I tried _id.getTimestamp() on a MongoDB _id in which "timestamp: true" is not passed as a parameter, but is still returning the timestamp.

So, is it truly necessary or does it have any other use other than storing the time of creation?

Harsh Verma • May 6 '20

timestamp : true, creates a createdAt and updatedAt field while your inserting documents in the document itself, by default it is not added.

The latter getTimestamp() is a function which finds created date. So there is a difference.

JatinRanka • May 10 '20

I think you interpreted my doubt in the wrong way.

I didn't pass "timestamps: true" as a parameter. And still, it returned the createdAt field when I tried "_id.getTimestamp()". Then what is the use of passing "timestamps: true" as a parameter?

Harsh Verma • May 10 '20 • Edited

Lets take a sample model for a signup in mongoose -->
var userSchema = new Schema({
email : String,
password : String,
fullName : String,
userName : {
type : String,
unique : true
}
})

This piece of code will create a mongodb document of this format -->
{
"id" : ObjectId("5eac7f0101dce40f15a97e8d"),
"email" : "asd@asd.com",
"userName" : "hv98",
"fullName" : "asd",
"password" : "asd",
"_v" : 0
}

Notice this doesn't have the createdAt and updatedAt fields

Now a sample model with the timestamp true field -->

var imageSchema = new Schema({
username : String,
description : String,
imagePath : {
type : String
},
comments : [commentSchema],
likes : [String],
nsfw : {
type : Boolean,
default : false
}

},{
timestamps : true
})

A document from this model would look like this -->
"id" : ObjectId("5eb02f999a15002d41f83e14"),
"likes" : [
"hv98"
],
"nsfw" : false,
"username" : "hv98",
"description" : "d",
"imagePath" : "1588604825052IMG_3265.JPG",
"comments" : [
{
"_id" : ObjectId("5eb1581ff810f83199fca925"),
"username" : "hv98",
"comment" : "dd",
"updatedAt" : ISODate("2020-05-05T12:12:15.736Z"),
"createdAt" : ISODate("2020-05-05T12:12:15.736Z")
}
],
"createdAt" : ISODate("2020-05-04T15:07:05.068Z"),
"updatedAt" : ISODate("2020-05-05T12:20:37.408Z"),
"_v" : 0
}

Now if you notice this document has a field called createdAt and updatedAt which was not the case in the earlier one

So when you use _id.getTimestamp() you get the timestamp but it is not a field which is already present in the document but something which the function does and if you have the timestamp : true then this is a field in the document and doesn't require an extra function to be called.

I hope this can settle the difference.

Edit -- **
**One of the uses of the createdAt field is displaying the documents in ascending or descending order.
eg code -->
Image.find({}).sort({ createdAt: -1 }).exec(function(err, docs) {
if(err) console.log(err);
res.json(docs);
});

This returns all the documents and sort them in ascending order that is the latest doc is displayed first and sends it to your client.

JatinRanka • May 10 '20 • Edited

Amazing explanation Harsh. This cleared all my doubts.

Armel • May 6 '20

Thanks for the reply Harsh ;)