joi

What is joi?

The Joi package is a powerful schema description language and data validator for JavaScript. It allows developers to create blueprints or schemas for JavaScript objects to ensure validation of key information. It is commonly used for validating data, such as configuration objects, request data in web applications, and more.

What are joi's main functionalities?

Object Schema Validation

This feature allows you to define a schema for an object, specifying the expected type of each property, and then validate data against this schema. The code sample demonstrates creating a schema for user data and validating an object against it.

{"const Joi = require('joi');\nconst schema = Joi.object({\n  username: Joi.string().alphanum().min(3).max(30).required(),\n  password: Joi.string().pattern(new RegExp('^[a-zA-Z0-9]{3,30}$')),\n  repeat_password: Joi.ref('password'),\n  access_token: [Joi.string(), Joi.number()],\n  birth_year: Joi.number().integer().min(1900).max(2013),\n  email: Joi.string().email({ minDomainSegments: 2, tlds: { allow: ['com', 'net'] } })\n}).with('username', 'birth_year');\n\nconst dataToValidate = {\n  username: 'abc',\n  birth_year: 1994,\n  email: '[e-mail]'\n};\n\nconst result = schema.validate(dataToValidate);\nconsole.log(result);"}

Type Casting

Joi can cast values to other types as part of the validation process. In this example, a string representing a number is cast to an actual number, and a string 'TRUE' is cast to a boolean true.

{"const Joi = require('joi');\nconst schema = Joi.object({\n  age: Joi.number().integer(),\n  active: Joi.string().trim().lowercase().valid('true', 'false').truthy('true').falsy('false').default(false).cast('boolean')\n});\n\nconst dataToValidate = {\n  age: '30',\n  active: 'TRUE'\n};\n\nconst result = schema.validate(dataToValidate, { convert: true });\nconsole.log(result.value); // { age: 30, active: true }"}

Custom Validation Messages

Joi allows you to specify custom validation messages for when data does not conform to the schema. This example shows how to set a custom message for a string that is too short.

{"const Joi = require('joi');\nconst schema = Joi.string().min(10).message('The string needs to be at least 10 characters long.');\n\nconst result = schema.validate('short');\nconsole.log(result.error); // Custom error message"}

Other packages similar to joi

yup

Yup is a JavaScript schema builder for value parsing and validation. It is similar to Joi but is leaner and designed for browser usage as well as Node.js. It uses a similar API to Joi but is built with a different focus on client-side validation.

ajv

Ajv (Another JSON Schema Validator) is a fast JSON schema validator supporting JSON Schema draft-06/07/2019-09/2020-12 and JSON Type Definition (RFC 8927). It is different from Joi in that it uses a JSON-based schema definition rather than a fluent API.

validator

Validator is a library of string validators and sanitizers. It is not a schema-based validation library like Joi but provides a set of string validation functions that can be used individually to validate specific types of input data.

class-validator

Class-validator works with TypeScript and uses decorators to define validation rules within class definitions. It is different from Joi in that it integrates tightly with TypeScript and leverages its type system for validation.

README

Object schema description language and validator for JavaScript objects.

Current version: 4.7.x

Lead Maintainer: Nicolas Morel

Table of Contents

- [Example](#example) - [Usage](#usage) - [`validate(value, schema, [options], [callback])`](#validatevalue-schema-options-callback) - [`compile(schema)`](#compileschema) - [`assert(value, schema, [message])`](#assertvalue-schema-message) - [`any`](#any) - [`any.allow(value)`](#anyallowvalue) - [`any.valid(value)`](#anyvalidvalue) - [`any.invalid(value)`](#anyinvalidvalue) - [`any.required()`](#anyrequired) - [`any.optional()`](#anyoptional) - [`any.forbidden()`](#anyforbidden) - [`any.description(desc)`](#anydescriptiondesc) - [`any.notes(notes)`](#anynotesnotes) - [`any.tags(tags)`](#anytagstags) - [`any.meta(meta)`](#anymetameta) - [`any.example(value)`](#anyexamplevalue) - [`any.unit(name)`](#anyunitname) - [`any.options(options)`](#anyoptionsoptions) - [`any.strict()`](#anystrict) - [`any.default(value)`](#anydefaultvalue) - [`any.concat(schema)`](#anyconcatschema) - [`any.when(ref, options)`](#anywhenref-options) - [`any.label(name)`](#anylabelname) - [`array`](#array) - [`array.includes(type)`](#arrayincludestype) - [`array.excludes(type)`](#arrayexcludestype) - [`array.min(limit)`](#arrayminlimit) - [`array.max(limit)`](#arraymaxlimit) - [`array.length(limit)`](#arraylengthlimit) - [`array.unique()`](#arrayunique) - [`binary`](#binary) - [`binary.encoding(encoding)`](#binaryencodingencoding) - [`binary.min(limit)`](#binaryminlimit) - [`binary.max(limit)`](#binarymaxlimit) - [`binary.length(limit)`](#binarylengthlimit) - [`boolean()`](#boolean) - [`date`](#date) - [`date.min(date)`](#datemindate) - [`date.max(date)`](#datemaxdate) - [`date.format(format)`](#dateformatformat) - [`date.iso()`](#dateiso) - [`func`](#func) - [`number`](#number) - [`number.min(limit)`](#numberminlimit) - [`number.max(limit)`](#numbermaxlimit) - [`number.greater(limit)`](#numbergreaterlimit) - [`number.less(limit)`](#numberlesslimit) - [`number.integer()`](#numberinteger) - [`number.precision(limit)`](#numberprecisionlimit) - [`object`](#object) - [`object.keys([schema])`](#objectkeysschema) - [`object.min(limit)`](#objectminlimit) - [`object.max(limit)`](#objectmaxlimit) - [`object.length(limit)`](#objectlengthlimit) - [`object.pattern(regex, schema)`](#objectpatternregex-schema) - [`object.and(peers)`](#objectandpeers) - [`object.nand(peers)`](#objectnandpeers) - [`object.or(peers)`](#objectorpeers) - [`object.xor(peers)`](#objectxorpeers) - [`object.with(key, peers)`](#objectwithkey-peers) - [`object.without(key, peers)`](#objectwithoutkey-peers) - [`object.rename(from, to, [options])`](#objectrenamefrom-to-options) - [`object.assert(ref, schema, [message])`](#objectassertref-schema-message) - [`object.unknown([allow])`](#objectunknownallow) - [`string`](#string) - [`string.insensitive()`](#stringinsensitive) - [`string.min(limit, [encoding])`](#stringminlimit-encoding) - [`string.max(limit, [encoding])`](#stringmaxlimit-encoding) - [`string.creditCard()`](#stringcreditCard) - [`string.length(limit, [encoding])`](#stringlengthlimit-encoding) - [`string.regex(pattern, [name])`](#stringregexpattern) - [`string.alphanum()`](#stringalphanum) - [`string.token()`](#stringtoken) - [`string.email()`](#stringemail) - [`string.guid()`](#stringguid) - [`string.hostname()`](#stringhostname) - [`string.lowercase()`](#stringlowercase) - [`string.uppercase()`](#stringuppercase) - [`string.trim()`](#stringtrim) - [`alternatives`](#alternatives) - [`alternatives.try(schemas)`](#alternativestryschemas) - [`alternatives.when(ref, options)`](#alternativeswhenref-options) - [`ref(key, [options])`](#refkey-options)

Example

var Joi = require('joi');

var schema = Joi.object().keys({
    username: Joi.string().alphanum().min(3).max(30).required(),
    password: Joi.string().regex(/[a-zA-Z0-9]{3,30}/),
    access_token: [Joi.string(), Joi.number()],
    birthyear: Joi.number().integer().min(1900).max(2013),
    email: Joi.string().email()
}).with('username', 'birthyear').without('password', 'access_token');

Joi.validate({ username: 'abc', birthyear: 1994 }, schema, function (err, value) { });  // err === null -> valid

The above schema defines the following constraints:

• username
  • a required string
  • must contain only alphanumeric characters
  • at least 3 characters long but no more than 30
  • must be accompanied by birthyear
• password
  • an optional string
  • must satisfy the custom regex
  • cannot appear together with access_token
• access_token
  • an optional, unconstrained string or number
• birthyear
  • an integer between 1900 and 2013
• email
  • a valid email address string

Usage

Usage is a two steps process. First, a schema is constructed using the provided types and constraints:

var schema = {
    a: Joi.string()
};

Note that joi schema objects are immutable which means every additional rule added (e.g. .min(5)) will return a new schema object.

Then the value is validated against the schema:

Joi.validate({ a: 'a string' }, schema, function (err, value) { });

If the value is valid, null is returned, otherwise an Error object.

The schema can be a plain JavaScript object where every key is assigned a joi type, or it can be a joi type directly:

var schema = Joi.string().min(10);

If the schema is a joi type, the schema.validate(value, callback) can be called directly on the type. When passing a non-type schema object, the module converts it internally to an object() type equivalent to:

var schema = Joi.object().keys({
    a: Joi.string()
});

When validating a schema:

• Keys are optional by default.
• Strings are utf-8 encoded by default.
• Rules are defined in an additive fashion and evaluated in order after whitelist and blacklist checks.

validate(value, schema, [options], [callback])

Validates a value using the given schema and options where:

• value - the value being validated.
• schema - the validation schema. Can be a joi type object or a plain object where every key is assigned a joi type object.
• options - an optional object with the following optional keys:
  • abortEarly - when true, stops validation on the first error, otherwise returns all the errors found. Defaults to true.
  • convert - when true, attempts to cast values to the required types (e.g. a string to a number). Defaults to true.
  • allowUnknown - when true, allows object to contain unknown keys which are ignored. Defaults to false.
  • skipFunctions - when true, ignores unknown keys with a function value. Defaults to false.
  • stripUnknown - when true, unknown keys are deleted (only when value is an object). Defaults to false.
  • language - overrides individual error messages, when 'label' is set, it overrides the key name in the error message. Defaults to no override ({}).
  • presence - sets the default presence requirements. Supported modes: 'optional', 'required', and 'forbidden'. Defaults to 'optional'.
  • context - provides an external data set to be used in references. Can only be set as an external option to validate() and not using any.options().
• callback - the optional synchronous callback method using the signature function(err, value) where:
  • err - if validation failed, the error reason, otherwise null.
  • value - the validated value with any type conversions and other modifiers applied (the input is left unchanged). value can be incomplete if validation failed and abortEarly is true. If callback is not provided, then returns an object with error and value properties.

var schema = {
    a: Joi.number()
};

var value = {
    a: '123'
};

Joi.validate(value, schema, function (err, value) { });
// err -> null
// value.a -> 123 (number, not string)

// or
var result = Joi.validate(value, schema);
// result.error -> null
// result.value -> { "a" : 123 }

compile(schema)

Converts literal schema definition to joi schema object (or returns the same back if already a joi schema object) where:

• schema - the schema definition to compile.

var definition = ['key', 5, { a: true, b: [/^a/, 'boom'] }];
var schema = Joi.compile(definition);

// Same as:

var schema = Joi.alternatives().try([
    Joi.string().valid('key'),
    Joi.number().valid(5),
    Joi.object().keys({
        a: Joi.boolean().valid(true),
        b: Joi.alternatives().try([
            Joi.string().regex(/^a/),
            Joi.string().valid('boom')
        ])
    })
]);

assert(value, schema, [message])

Validates a value against a schema and throws if validation fails where:

• value - the value to validate.
• schema - the schema object.
• message - optional message sting prefix added in front of the error message.

Joi.assert('x', Joi.number());

any

Generates a schema object that matches any data type.

var any = Joi.any();
any.validate('a', function (err, value) { });

any.allow(value)

Whitelists a value where:

• value - the allowed value which can be of any type and will be matched against the validated value before applying any other rules. value can be an array of values, or multiple values can be passed as individual arguments. value supports references.

var schema = {
    a: Joi.any().allow('a'),
    b: Joi.any().allow('b', 'B'),
    c: Joi.any().allow(['c', 'C'])
};

any.valid(value)

Adds the provided values into the allowed whitelist and marks them as the only valid values allowed where:

• value - the allowed value which can be of any type and will be matched against the validated value before applying any other rules. value can be an array of values, or multiple values can be passed as individual arguments. value supports references.

var schema = {
    a: Joi.any().valid('a'),
    b: Joi.any().valid('b', 'B'),
    c: Joi.any().valid(['c', 'C'])
};

any.invalid(value)

Blacklists a value where:

• value - the forbidden value which can be of any type and will be matched against the validated value before applying any other rules. value can be an array of values, or multiple values can be passed as individual arguments. value supports references.

var schema = {
    a: Joi.any().invalid('a'),
    b: Joi.any().invalid('b', 'B'),
    c: Joi.any().invalid(['c', 'C'])
};

any.required()

Marks a key as required which will not allow undefined as value. All keys are optional by default.

var schema = Joi.any().required();

any.optional()

Marks a key as optional which will allow undefined as values. Used to annotate the schema for readability as all keys are optional by default.

var schema = Joi.any().optional();

any.forbidden()

Marks a key as forbidden which will not allow any value except undefined. Used to explicitly forbid keys.

var schema = {
    a: Joi.any().forbidden()
};

any.description(desc)

Annotates the key where:

• desc - the description string.

var schema = Joi.any().description('this key will match anything you give it');

any.notes(notes)

Annotates the key where:

• notes - the notes string or array of strings.

var schema = Joi.any().notes(['this is special', 'this is important']);

any.tags(tags)

Annotates the key where:

• tags - the tag string or array of strings.

var schema = Joi.any().tags(['api', 'user']);

any.meta(meta)

Attaches metadata to the key where:

• meta - the meta object to attach.

var schema = Joi.any().meta({ index: true });

any.example(value)

Annotates the key where:

• value - an example value.

If the example fails to pass validation, the function will throw.

var schema = Joi.string().min(4).example('abcd');

any.unit(name)

Annotates the key where:

• name - the unit name of the value.

var schema = Joi.number().unit('milliseconds');

any.options(options)

Overrides the global validate() options for the current key and any sub-key where:

• options - an object with the same optional keys as Joi.validate(value, schema, options, callback).

var schema = Joi.any().options({ convert: false });

any.strict()

Sets the options.convert options to false which prevent type casting for the current key and any child keys.

var schema = Joi.any().strict();

any.default(value)

Sets a default value if the original value is undefined where:

• value - the value. value supports references.

Note that if value is an object, any changes to the object after default() is called will change the reference and any future assignment.

var schema = {
    username: Joi.string().default('new_user')
};
Joi.validate({}, schema, function (err, value) { });
// value === { username: "new_user" }

any.concat(schema)

Returns a new type that is the result of adding the rules of one type to another where:

• schema - a joi type to merge into the current schema. Can only be of the same type as the context type or any.

var a = Joi.string().valid('a');
var b = Joi.string().valid('b');
var ab = a.concat(b);

any.when(ref, options)

Converts the type into an alternatives type where the conditions are merged into the type definition where:

• ref - the key name or reference.
• options - an object with:
  • is - the required condition joi type.
  • then - the alternative schema type if the condition is true. Required if otherwise is missing.
  • otherwise - the alternative schema type if the condition is false. Required if then is missing.

var schema = {
    a: Joi.any().valid('x').when('b', { is: 5, then: Joi.valid('y'), otherwise: Joi.valid('z') }),
    b: Joi.any()
};

Alternatively, if you want to specify a specific type such as string, array, etc, you can do so like this:

var schema = {
    a: Joi.valid('a', 'b', 'other'),
    other: Joi.string()
        .when('a', { is: 'other', then: Joi.required() }),
};

any.label(name)

Overrides the key name in error messages.

• name - the name of the key.

var schema = {
    first_name: Joi.string().label('First Name')
};

array

Generates a schema object that matches an array data type.

Supports the same methods of the any() type.

var array = Joi.array().includes(Joi.string().valid('a', 'b'));
array.validate(['a', 'b', 'a'], function (err, value) { });

array.includes(type)

List the types allowed for the array values where:

• type - a joi schema object to validate each array item against. type can be an array of values, or multiple values can be passed as individual arguments.

var schema = Joi.array().includes(Joi.string(), Joi.number());

array.excludes(type)

List the types forbidden for the array values where:

• type - a joi schema object to validate each array item against. type can be an array of values, or multiple values can be passed as individual arguments.

var schema = Joi.array().excludes(Joi.object());

array.min(limit)

Specifies the minimum number of items in the array where:

• limit - the lowest number of array items allowed.

var schema = Joi.array().min(2);

array.max(limit)

Specifies the maximum number of items in the array where:

• limit - the highest number of array items allowed.

var schema = Joi.array().max(10);

array.length(limit)

Specifies the exact number of items in the array where:

• limit - the number of array items allowed.

var schema = Joi.array().length(5);

array.unique()

Requires the array values to be unique. Only works for literals (numbers and strings), all other types are ignored.

var schema = Joi.array().unique();

boolean

Generates a schema object that matches a boolean data type (as well as the strings 'true', 'false', 'yes', and 'no'). Can also be called via bool().

Supports the same methods of the any() type.

var boolean = Joi.boolean();
boolean.validate(true, function (err, value) { });

binary

Generates a schema object that matches a Buffer data type (as well as the strings which will be converted to Buffers).

Supports the same methods of the any() type.

var schema = Joi.binary();

binary.encoding(encoding)

Sets the string encoding format if a string input is converted to a buffer where:

• encoding - the encoding scheme.

var schema = Joi.binary().encoding('base64');

binary.min(limit)

Specifies the minimum length of the buffer where:

• limit - the lowest size of the buffer.

var schema = Joi.binary().min(2);

binary.max(limit)

Specifies the maximum length of the buffer where:

• limit - the highest size of the buffer.

var schema = Joi.binary().max(10);

binary.length(limit)

Specifies the exact length of the buffer:

• limit - the size of buffer allowed.

var schema = Joi.binary().length(5);

date

Generates a schema object that matches a date type (as well as a JavaScript date string or number of milliseconds).

Supports the same methods of the any() type.

var date = Joi.date();
date.validate('12-21-2012', function (err, value) { });

date.min(date)

Specifies the oldest date allowed where:

• date - the oldest date allowed.

var schema = Joi.date().min('1-1-1974');

Note: 'now' can be passed in lieu of date so as to always compare relatively to the current date, allowing to explicitly ensure a date is either in the past or in the future.

var schema = Joi.date().min('now');

date.max(date)

Specifies the latest date allowed where:

• date - the latest date allowed.

var schema = Joi.date().max('12-31-2020');

Note: 'now' can be passed in lieu of date so as to always compare relatively to the current date, allowing to explicitly ensure a date is either in the past or in the future.

var schema = Joi.date().max('now');

date.format(format)

Specifies the allowed date format:

• format - string or array of strings that follow the moment.js format.

var schema = Joi.date().format('YYYY/MM/DD');

date.iso()

Requires the string value to be in valid ISO 8601 date format.

var schema = Joi.date().iso();

func

Generates a schema object that matches a function type.

Supports the same methods of the any() type.

var func = Joi.func();
func.validate(function () {}, function (err, value) { });

number

Generates a schema object that matches a number data type (as well as strings that can be converted to numbers).

Supports the same methods of the any() type.

var number = Joi.number();
number.validate(5, function (err, value) { });

number.min(limit)

Specifies the minimum value where:

• limit - the minimum value allowed.

var schema = Joi.number().min(2);

number.max(limit)

Specifies the maximum value where:

• limit - the maximum value allowed.

var schema = Joi.number().max(10);

number.greater(limit)

Specifies that the value must be greater than limit.

var schema = Joi.number().greater(5);

number.less(limit)

Specifies that the value must be less than limit.

var schema = Joi.number().less(10);

number.integer()

Requires the number to be an integer (no floating point).

var schema = Joi.number().integer();

number.precision(limit)

Specifies the maximum number of decimal places where:

• limit - the maximum number of decimal places allowed.

var schema = Joi.number().precision(2);

object

Generates a schema object that matches an object data type (as well as JSON strings that parsed into objects). Defaults to allowing any child key.

Supports the same methods of the any() type.

var object = Joi.object().keys({
    a: Joi.number().min(1).max(10).integer(),
    b: 'some string'
});

object.validate({ a: 5 }, function (err, value) { });

object.keys([schema])

Sets or extends the allowed object keys where:

• schema - optional object where each key is assigned a joi type object. If schema is {} no keys allowed. If schema is null or undefined, any key allowed. If schema is an object with keys, the keys are added to any previously defined keys (but narrows the selection if all keys previously allowed). Defaults to 'undefined' which allows any child key.

var base = Joi.object().keys({
    a: Joi.number(),
    b: Joi.string()
});
// Validate keys a, b and c.
var extended = base.keys({
    c: Joi.boolean()
});

object.min(limit)

Specifies the minimum number of keys in the object where:

• limit - the lowest number of keys allowed.

var schema = Joi.object().min(2);

object.max(limit)

Specifies the maximum number of keys in the object where:

• limit - the highest number of object keys allowed.

var schema = Joi.object().max(10);

object.length(limit)

Specifies the exact number of keys in the object where:

• limit - the number of object keys allowed.

var schema = Joi.object().length(5);

object.pattern(regex, schema)

Specify validation rules for unknown keys matching a pattern where:

• regex - a regular expression tested against the unknown key names.
• schema - the schema object matching keys much validate against.

var schema = Joi.object({
    a: Joi.string()
}).pattern(/\w\d/, Joi.boolean());

object.and(peers)

Defines an all-or-nothing relationship between keys where if one of the peers is present, all of them are required as well where:

• peers - the key names of which if one present, all are required. peers can be a single string value, an array of string values, or each peer provided as an argument.

var schema = Joi.object().keys({
    a: Joi.any(),
    b: Joi.any()
}).and('a', 'b');

object.nand(peers)

Defines a relationship between keys where not all peers can be present at the same time where:

• peers - the key names of which if one present, the others may not all be present. peers can be a single string value, an array of string values, or each peer provided as an argument.

var schema = Joi.object().keys({
    a: Joi.any(),
    b: Joi.any()
}).nand('a', 'b');

object.or(peers)

Defines a relationship between keys where one of the peers is required (and more than one is allowed) where:

• peers - the key names of which at least one must appear. peers can be a single string value, an array of string values, or each peer provided as an argument.

var schema = Joi.object().keys({
    a: Joi.any(),
    b: Joi.any()
}).or('a', 'b');

object.xor(peers)

Defines an exclusive relationship between a set of keys where one of them is required but not at the same time where:

• peers - the exclusive key names that must not appear together but where one of them is required. peers can be a single string value, an array of string values, or each peer provided as an argument.

var schema = Joi.object().keys({
    a: Joi.any(),
    b: Joi.any()
}).xor('a', 'b');

object.with(key, peers)

Requires the presence of other keys whenever the specified key is present where:

• key - the reference key.
• peers - the required peer key names that must appear together with key. peers can be a single string value or an array of string values.

Note that unlike object.and(), with() creates a dependency only between the key and each of the peers, not between the peers themselves.

var schema = Joi.object().keys({
    a: Joi.any(),
    b: Joi.any()
}).with('a', 'b');

object.without(key, peers)

Forbids the presence of other keys whenever the specified is present where:

• key - the reference key.
• peers - the forbidden peer key names that must not appear together with key. peers can be a single string value or an array of string values.

var schema = Joi.object().keys({
    a: Joi.any(),
    b: Joi.any()
}).without('a', ['b']);

object.rename(from, to, [options])

Renames a key to another name (deletes the renamed key) where:

• from - the original key name.
• to - the new key name.
• options - an optional object with the following optional keys:
  • alias - if true, does not delete the old key name, keeping both the new and old keys in place. Defaults to false.
  • multiple - if true, allows renaming multiple keys to the same destination where the last rename wins. Defaults to false.
  • override - if true, allows renaming a key over an existing key. Defaults to false.

Keys are renamed before any other validation rules are applied.

var object = Joi.object().keys({
    a: Joi.number()
}).rename('b', 'a');

object.validate({ b: 5 }, function (err, value) { });

object.assert(ref, schema, [message])

Verifies an assertion where:

• ref - the key name or reference.
• schema - the validation rules required to satisfy the assertion. If the schema includes references, they are resolved against the object value, not the value of the ref target.
• message - optional human-readable message used when the assertion fails. Defaults to 'failed to pass the assertion test'.

var schema = Joi.object().keys({
    a: {
        b: Joi.string(),
        c: Joi.number()
    },
    d: {
        e: Joi.any()
    }
}).assert('d.e', Joi.ref('a.c'), 'equal to a.c');

object.unknown([allow])

Overrides the handling of unknown keys for the scope of the current object only (does not apply to children) where:

• allow - if false, unknown keys are not allowed, otherwise unknown keys are ignored.

var schema = Joi.object({ a: Joi.any() }).unknown();

string

Generates a schema object that matches a string data type. Note that empty strings are not allowed by default and must be enabled with allow('').

Supports the same methods of the any() type.

var schema = Joi.string().min(1).max(10);
schema.validate('12345', function (err, value) { });

string.insensitive()

Allows the value to match any whitelist of blacklist item in a case insensitive comparison.

var schema = Joi.string().valid('a').insensitive();

string.min(limit, [encoding])

Specifies the minimum number string characters where:

• limit - the minimum number of string characters required.
• encoding - is specified, the string length is calculated in bytes using the provided encoding.

var schema = Joi.string().min(2);

string.max(limit, [encoding])

Specifies the maximum number of string characters where:

• limit - the maximum number of string characters allowed.
• encoding - is specified, the string length is calculated in bytes using the provided encoding.

var schema = Joi.string().max(10);

string.creditCard()

Requires the number to be a credit card number (Using Lunh Algorithm).

var schema = Joi.string().creditCard();

string.length(limit, [encoding])

Specifies the exact string length required where:

• limit - the required string length.
• encoding - is specified, the string length is calculated in bytes using the provided encoding.

var schema = Joi.string().length(5);

string.regex(pattern, [name])

Defines a regular expression rule where:

• pattern - a regular expression object the string value must match against.
• name - optional name for patterns (useful with multiple patterns). Defaults to 'required'.

var schema = Joi.string().regex(/^[abc]+$/);

string.alphanum()

Requires the string value to only contain a-z, A-Z, and 0-9.

var schema = Joi.string().alphanum();

string.token()

Requires the string value to only contain a-z, A-Z, 0-9, and underscore _.

var schema = Joi.string().token();

string.email()

Requires the string value to be a valid email address.

var schema = Joi.string().email();

string.guid()

Requires the string value to be a valid GUID.

var schema = Joi.string().guid();

string.hostname()

Requires the string value to be a valid hostname as per RFC1123.

var schema = Joi.string().hostname();

string.lowercase()

Requires the string value to be all lowercase. If the validation convert option is on (enabled by default), the string will be forced to lowercase.

var schema = Joi.string().lowercase();

string.uppercase()

Requires the string value to be all uppercase. If the validation convert option is on (enabled by default), the string will be forced to uppercase.

var schema = Joi.string().uppercase();

string.trim()

Requires the string value to contain no whitespace before or after. If the validation convert option is on (enabled by default), the string will be trimmed.

var schema = Joi.string().trim();

alternatives

Generates a type that will match one of the provided alternative schemas via the try() method. If no schemas are added, the type will not match any value except for undefined.

Supports the same methods of the any() type.

Alternatives can be expressed using the shorter [] notation.

var alt = Joi.alternatives().try(Joi.number(), Joi.string());
// Same as [Joi.number(), Joi.string()]

alternatives.try(schemas)

Adds an alternative schema type for attempting to match against the validated value where:

• schema - an array of alternative joi types. Also supports providing each type as a separate argument.

var alt = Joi.alternatives().try(Joi.number(), Joi.string());
alt.validate('a', function (err, value) { });

alternatives.when(ref, options)

Adds a conditional alternative schema type based on another key (not the same as any.when()) value where:

• ref - the key name or reference.
• options - an object with:
  • is - the required condition joi type.
  • then - the alternative schema type to try if the condition is true. Required if otherwise is missing.
  • otherwise - the alternative schema type to try if the condition is false. Required if then is missing.

var schema = {
    a: Joi.alternatives().when('b', { is: 5, then: Joi.string(), otherwise: Joi.number() }),
    b: Joi.any()
};

Note that when() only adds additional alternatives to try and does not impact the overall type. Setting a required() rule on a single alternative will not apply to the overall key. For example, this definition of a:

var schema = {
    a: Joi.alternatives().when('b', { is: true, then: Joi.required() }),
    b: Joi.boolean()
};

Does not turn a into a required key when b is true. Instead, it tells the validator to try and match the value to anything that's not undefined. However, since Joi.alternatives() by itself allows undefined, the rule does not accomplish turning a to a required value. This rule is the same as Joi.alternatives([Joi.required()]) when b is true which will allow any value including undefined.

To accomplish the desired result above use:

var schema = {
    a: Joi.when('b', { is: true, then: Joi.required() }),
    b: Joi.boolean()
};

ref(key, [options])

Generates a reference to the value of the named key. References are resolved at validation time and in order of dependency so that if one key validation depends on another, the dependent key is validated second after the reference is validated. References support the following arguments:

• key - the reference target. References cannot point up the object tree, only to sibling keys, but they can point to their siblings' children (e.g. 'a.b.c') using the . separator. If a key starts with $ is signifies a context reference which is looked up in the context option object.
• options - optional settings:
  • separator - overrides the default . hierarchy separator.
  • contextPrefix - overrides the default $ context prefix signifier.

Note that references can only be used where explicitly supported such as in valid() or invalid() rules. If upwards (parents) references are needed, use object.assert().

var schema = Joi.object().keys({
    a: Joi.ref('b.c'),
    b: {
        c: Joi.any()
    },
    c: Joi.ref('$x')
});

Joi.validate({ a: 5, b: { c: 5 } }, schema, { context: { x: 5 } }, function (err, value) {});