MongoDB 自动递增作为新用户的 ID

Question

I'm working on a small Web-API project using MongoDB. As far as I know, MongoDB uses _id:UnixDateETC but I want a ID that like in MySQL or MSQL is able to autoincrement each time a new user is created. I played around with the "find().count()", found some attemps on the internet, but none of what I tried seem to work. I'm not quite sure if I'm doing it wrong or if it's not possible by doing such thing like I tried them. ( My attempt can be found under "models/user.js":id)

Any suggestions how I directly can go into the schema, count it's entries and than add it to the new record without any complicated new seperate function ? The reason for that is that I'm trying to hold the models clean/readable.

Thanks in advance.

routes/user.js:

let mongoose = require('mongoose');
let User = require('../models/user');
var config = require('../configs/config');
var jwt = require('jsonwebtoken');
var bcrypt = require('bcryptjs');


function userRegistration(req, res) {
    var hashedPassword = bcrypt.hashSync(req.body.psw, 10);
    var user = new User(req.body);
    user.psw = hashedPassword;
        user.save(function (err) {      
            if (err) return res.status(500).send("There was a problem registering the user.");
            var token = jwt.sign({ id: user.userName }, config.secret, {
                    expiresIn: 86400 // expires in 24 hours
            });
                  res.status(200).send({ auth: true, token: token });        
  });
}

//export all the functions
module.exports = { userRegistration };

models/user.js:

var mongoose = require('mongoose');
var Schema = mongoose.Schema;


var UserSchema = new Schema({
    id: this.db.id.find().count() + 1,
    userName: String,
    psw: String,
    email: String , 
    active : Boolean
});




module.exports = mongoose.model('User', UserSchema);

Answer 1

Got it to work.

What I had to do was to create a preSave in my "/models/user.js"

model/user.js:

var mongoose = require('mongoose');
var Schema = mongoose.Schema;


var UserSchema = new Schema({
    id: Number,
    userName: String,
    psw: String,
    email: String , 
    active : Boolean
});


UserSchema.pre("save", function(next){
    var docs = this;
    mongoose.model('User', UserSchema).countDocuments(function(error, counter){
        if(error) return next(error);
        docs.id = counter+1;
        next();
    });   
});

##Edit 02.07.2021: Note that this solution only works aslong u clear or keep instead of deleting your document(s). Otherwise u will end up with duplicate ID's since I count the number of currently existing documents. Back then my final solution was to store a counter/value in another collection/table and increment it each time a new document gets created to keep track of my id(s). This newly incremented value will then be used in our preSave instead of counting documents...