How to create an Auto-Incrementing field in MongoDB?

Create an Auto-Incrementing

 I checked so many article related to this but all are confusing for me because i was new in MongoDB
and i want to create a field which should be auto increment like MySql.
So i got an article on docs.mongodb.org and find that this article is great

Here are some steps that how you can create an auto-increament id in your MongoDB

Open your MongoDB screen where you write command line query

Run this command and check database

Step 1. show dbs - This command will show all database from your MongoDB

Step 2. use databasename -  choose your database where you want to

create a collection and auto increment field

Now create new collection

Step 3. db.createCollection("user");

Step 4. db.counters.insert(

   {
      _id: "userid",
      seq: 0
   }
)

Now you need to create a function for auto increment the _id in mongoDB
so create a function in your mongodb
You need to write this function on your mongoDB screen just after the above command

Step 5. function getNextSequence(name) {

   var ret = db.counters.findAndModify(

          {

            query: { _id: name },

            update: { $inc: { seq: 1 } },

            new: true

          }

   );

   return ret.seq;

}

Step 6. db.user.insert(

   {

     _id: getNextSequence("userid"),

     name: "PHP developer"

   }

)

db.user.insert(

   {

     _id: getNextSequence("userid"),

     name: "Mongo Db developer"

   }

) 

Now you can check your record in your mongoDB with this command

db.users.find()

I hope you understand now that how its works!