MongoDB is a famous NoSQL Database. If you're just getting started with MongoDB, I would suggest you begin with Mongo University
Anatomy
MongoDB's ObjectID is made of 12 bytes. The 12 bytes consists of
a 4-byte timestamp.
a 5-byte random value generated once per process.
a 3-byte incrementing counter initialized to a random value.
Example:
65f87920068c7d17cb1288d6
65f87920 - Unix Epoch Timestamp
068c7d17cb - Random Value
1288d6 - Incrementing Counter
Constructing ObjectId
You can use the ObjectId() method to construct a new ObjectId.
Optionally, it can take two inputs.
hexadecimal - A 24-character hexadecimal string value.
integer - The integer value, in seconds, is added to the Unix epoch to create the new timestamp.
Example:
$ ObjectId(10)
ObjectId('0000000a0d098c2eda0f296e')
Methods you can use on ObjectId
getTimestamp()
Since the timestamp is included in the ObjectId, you can retrieve the time in which the ObjectId was generated.
$ ObjectId('665377378755af3d1e7c5701').getTimestamp()
2024-05-26T17:53:59.000Z
$ ObjectId('0000000a0d098c2eda0f296e').getTimestamp()
1970-01-01T00:00:10.000Z
toString()
You can use this method in case if you want to convert the ObjectId to hexadecimal string.
$ ObjectId('665b4d520d098c2eda0f296d').toString()
665b4d520d098c2eda0f296d