# xpress-mongo - Joi Schema

# What is Joi?

Joi (opens new window) is the most powerful schema description language and data validator for JavaScript.

# Why support Joi Schema?

Aside having a similar structure, The default xpress-mongo schema is focused more on data type check than data value validation. With Joi we can do more at validation level than just data checking.

For Example:

const {is} = require("xpress-mongo");

const UserSchema = {
  email: is.String().required(),

The schema above will check if the field email is a valid string but has no concern with checking if the string is really an email address. With Joi we can check if email is typeof "string", and a valid email address.

Like so:

// Joi is exported as `joi` in xpress-mongo >= 1.0.0
const {joi} = require("xpress-mongo");

const UserSchema = {
  email: joi.string().email().required(),

email will throw an error if not a string, and a valid email address.

# Validating Objects

The default schema, Just like the email example above, does NOT validate the keys in an object. It only checks if data passed is an object.

const {is} = require("xpress-mongo");

const UserSchema = {
  contact: is.Object(() => ({
    phone: null,
    website: null,

The schema above will NOT throw an error if phone or website does not exist. It only checks if contact is an object and will set the default passed if contact is undefined.

With Joi we can validate objects like so:

const {joi} = require("xpress-mongo");
const {urlRegex, phoneRegex} = require("./expressions");

const UserSchema = {
  contact: joi.object({
    // validate `contact.phone` with regex
    phone: joi.string().regex(phoneRegex).required(),
    // validate `contact.website` with regex
    website: joi.string().regex(urlRegex).required(),

# No Conflict

Both Default & Joi Schemas can be mixed up in a xpress-mongo schema object.

For example

const {is, joi} = require("xpress-mongo");

const UserSchema = {
  username: is.String().required(), // default
  email: joi.string().email().required(), // joi
  age: joi.number().greater(18).required(), // joi
  verified: is.Boolean().required() // default

# Performance

The default schema is faster because it only runs data type checks.

The Joi schema is slower and this is expected because it does more than just data type checks. Time difference is not noticeable unless you are updating/creating millions of documents.

# Joi Documentation

See joi.dev (opens new window)