how to insert autoincrement number with my mongoose collection

Question

I am newbie to mongoose, I have a mongoose schema like this:

var user = mongoose.Schema({
    userID: {
        type: String,
        required:true
    },
           


        

Answer 1

If you want an autoincrement prop based on the length of your collection, you can do something like this:

UserSchema.pre("save", function (next) {
  if (this.isNew) {
    this.constructor.find({}).then((users) => {
      this.autoIncrementProp = users.length + 1;
      next();
    });
  }
});

isNew is a reserved Schema name (Boolean flag specifying if the document is new.)