Create SchemaValidator

    const Joi = require('joi');

    const options = {
        abortEarly: false, // include all errors
        allowUnknown: true, // ignore unknown props
        stripUnknown: true // remove unknown props
    };

    class UserSchemaValidator {


         validateCreateUserSchema = async function (req,res,next){
           
           
            const schema = Joi.object({
                name: Joi.string().required(),
                email: Joi.string().email().required(),
                password: Joi.string().min(6).required(),
                role: Joi.string().valid('ADMIN', 'USER').required()
            });

            try{
                let result = await schema.validateAsync(req.body, options);
                console.log("Result:", result);
                next();
            }
            catch(error){    
                let errorMessages = error.details.map(x=> ({ field: x.path[0], message: x.message}));             
                console.error(JSON.stringify(errorMessages));
                let result = { status: 400, errors: errorMessages};
                res.status(400).json(result);
            }
        }   
    }

    exports.UserSchemaValidator = UserSchemaValidator;

Use Schema Validator in router.js

    const express = require('express');
    const router = express.Router();

    const {UserSchemaValidator}  = require('./user.schema.validator');

    // routes
    const userSchemaValidator =  new UserSchemaValidator();
    router.post('/api/users/', userSchemaValidator.validateCreateUserSchema, createUser);

    function createUser(req,res){
        let user = req.body;
        res.status(200).json(user);
    }


    module.exports = router;

Run the server - app.js

    const express = require('express');
    const router = require('./router');
    const app = express();
    app.use(express.json());
    app.use(express.urlencoded({ extended: false }));

    app.use('/', router);
    const port = 3000
    app.listen(port, () => {
        console.log(`Server listening at http://localhost:${port}`)
    })

Test the API in POSTMAN Tool

• http://localhost:3000/api/users ( POST)

     { name:"Naresh", email:"", password:"1", role:"USER"}

Response Error Messages

    {
        "status": 400,
        "errors": [
            {
                "field": "email",
                "message": "\"email\" is not allowed to be empty"
            },
            {
                "field": "password",
                "message": "\"password\" length must be at least 6 characters long"
            }
        ]
    }