1 Validation Schema

const Joi = require("joi");

const registerValidationSchema = Joi.object().keys({
  name: Joi.string()
    .min(2)
    .max(30)
    .required(),
  email: Joi.string()
    .email()
    .required(),
  password: Joi.string()
    .min(6)
    .required()
});

module.exports = registerValidationSchema;

2 Route

router.post("/register", (req, res, next) => {
  const userProps = req.body;
  const { email } = userProps;

  User.findOne({ email })
    .then(user => {
      if (user) {
        return res.status(400).json({ errormessage: "User already exists." });
      } else {
        const avatar = gravatar.url(email, {
          s: "200", // Size
          r: "pg", // Rating
          d: "mm" // Default
        });

        const newUser = new User({ ...userProps, avatar });

        Joi.validate(newUser, userValidationSchema, {
          abortEarly: false
        });

        bcrypt.genSalt(10, (err, salt) => {
          bcrypt.hash(newUser.password, salt, (err, hash) => {
            if (err) {
              next(err);
            }
            newUser.password = hash;
            newUser
              .save()
              .then(user => res.json(user))
              .catch(err => res.status(400).json(err));
          });
        });
      }
    })
    .catch(next);
});

3 Returned Validation Error Obj

{
    "errors": {
        "name": {
            "message": "Path `name` is required.",
            "name": "ValidatorError",
            "properties": {
                "message": "Path `name` is required.",
                "type": "required",
                "path": "name",
                "value": ""
            },
            "kind": "required",
            "path": "name",
            "value": ""
        },
        "email": {
            "message": "Path `email` is required.",
            "name": "ValidatorError",
            "properties": {
                "message": "Path `email` is required.",
                "type": "required",
                "path": "email",
                "value": ""
            },
            "kind": "required",
            "path": "email",
            "value": ""
        }
    },
    "_message": "users validation failed",
    "message": "users validation failed: name: Path `name` is required., email: Path `email` is required.",
    "name": "ValidationError"
}