Validate the Mongoose Schema with Joi Library

`"use strict";

import mongoose from "mongoose";
import Joi from "joi";

const userSchema = mongoose.Schema({
username: { type: String, required: true },
password: { type: String, required: true },
email: { type: String, required: true },
createdAt: { type: Date, default: Date.now }
});

userSchema.methods.joiValidate = function(obj) {
var schema = {
username: Joi.types
.String()
.min(6)
.max(30)
.required(),
password: Joi.types
.String()
.min(8)
.regex(/[a-zA-Z0-9]{3,30}/)
.required(),
email: Joi.types
.String()
.email()
.required(),
createdAt: Joi.types.Date()
};
return Joi.validate(obj, schema);
};

export default mongoose.model("User", userSchema);
`