indicative

Indicative

Indicative is an expressive Javascript validator for humans. Improve your workflow by removing all unnecessary curly braces and nested declarations. Under the hood indicative has following.

• Schema validator to validate an data object.
• It has support for nested validations.
• Custom messages for validations and rules.
• Raw validator for quick if validations
• Data Sanitization
• Return promises
• Es6 generators friendly.

Installation

Installing indicative requires node 4.0 or greater with npm installed.

npm i --save indicative

Basics

Indicative is an expressive schema/raw validator for NodeJs and offers clean syntax over snake of curly braces.To validate an object of data, you need to define a schema where each field can have multiple rules.

Setup

You start by requiring indicative and then make use of multiple methods to validate a data object with schema definition.

const indicative = require('indicative')

validate (data, rules, [messages])

Validate method will run the validation cycle, which gets terminated on the first error.

const rules = {
  username: 'required'
}

const data = {
  username: null
}

indicative
.validate(data, rules)
.then(function () {
  // validation passed
})
.catch(function (errors) {
  // validation failed
})

validateAll (data, rules, [messages])

Validate all will validate all fields even after errors are thrown and return an array of error messages.

indicative.validateAll(data, rules)

Rules

Indicative helps you in defining rules as a string, which makes it more readable and remove unnecessary curly braces from your schema definition.

A rule is a combination of certain logical expression that are parsed by a parser before starting validation.

1. | - A pipe symbol ( | ) is used to define multiple rules
2. : - A colon ( : ) is used to define values next to your rules
3. , - And a comma ( , ) is used to define multiple values next to your rules.

basic rule

A basic rule may look like this, where we define multiple rules by separating them with a pipe symbol.

{
  email_address: 'required|email'
}

rule with values

A complex rule can have values defined next to rule definition, which later will be used to run validations.

{
  age: 'required|above:18'
}

Define age is separated by the colon on above rule. Also, some rules can accept multiple values next to a given rule.

{
  age: 'required|range:18,40'
}

Schema

Schema definition is an object containing multiple rules for multiple fields and is used by validation methods.

const rules = {
  username  : 'required|alpha_numeric',
  email     : 'required|email',
  password  : 'required|min:6|max:30'
}

Schema object is a set of different rules defined for different fields and in order to validate an object of data you need to pass rules and data together to validate method.

const rules = {
  username  : 'required|alpha_numeric',
  email     : 'required|email',
  password  : 'required|min:6|max:30'
}

const data = {
  username  : 'doe22',
  email     : '[e-mail]',
  password  : 'doe123456'
}

indicative
.validate(data, rules)
.then(function () {
  // validation passed
})
.catch(function (errors) {
  // validation failed
})

nested rules

In order to validate nested data you need to make use of dot-notation to target nested fields inside data object.

const rules = {
  'profile.username'  : 'required',
  'profile.password'  : 'required|min:6|max:30'
}

const data = {
  profile:{
    username  : 'doe22',
    password  : 'doe123456'
  }
}

Here dot-notation will help you in removing the use of unnecessary curly braces and can target nested data to any given number of levels.

Custom messages

Indicative self-constructs error messages when validation for a given rule fails, which may not be helpful when trying to keep error messages descriptive and personalised.

global messages

Global messages are defined on rules, and the same message will be used whenever a rule will fail.

const messages = {
  required: 'This field is required to complete the registration process.'
}

indicative
.validate(data, rules, messages)
.then(function () {
  // validation passed
})
.catch(function (errors) {
  // validation failed
})

Whenever a required rule fails, it will return your custom message instead of a self-constructed message.

field specific messages.

field specific messages are even more personalised as they are defined for a given rule and field.

const messages = {
  'username.required' : 'Username is required to continue',
  'email.required'    : 'Email is required for further communication'
}


indicative
.validate(data, rules, messages)
.then(function () {
  // validation passed
})
.catch(function (errors) {
  // validation failed
})

Also, you can make use of dot-notation while defining messages.

const messages = {
  'profile.username.required': 'Username is required to setup profile'
}

getters

instead of defining a string as a message, you can also define a function to return message

const messages = {
  'username.required': function (field, validation, args) {
    return `${field} is required`
  }
}

Templating

All custom messages support templating, which means you can define special placeholders that will be replaced with actual values while constructing messages.

field

field is the name of the field under validation

const messages = {
  required: '{{field}} is required to complete registeration process'
}

validation

Name of the validation rule.

const messages = {
  email: '{{validation}} validation failed on {{field}}.'
}

const data = {
  email: 'abc'
}

argument

arguments are values defined on rules inside schema, and they can be accessed using their array index.

const messages = {
  above: '{{field}} must be over {{argument.0}} years'
}

const rules = {
  age: 'above:18'
}

const data = {
  age: 10
}

Above message will yield age must be over 18 years.

Array Expressions

Validating arrays asynchronously is never fun. Indicative makes it so simple to validating one level deep nested arrays using array expressions.

const rules = {
  'users.*.username': 'required|alpha',
  'users.*.email': 'required|email'
}

const data = {
  users: [
    {
      username: 'validUsername',
      email: '[e-mail]'
    },
    {
      username: '123Invalid',
      email: 'bar.com'
    }
  ]
}

indicative
.validate(data, rules)
.then(function () {
  // validation passed
})
.catch(function (errors) {
  // validation failed
})

Also you can validate flat arrays using the same expression syntax.

const rules = {
  'emails': 'array|min:2',
  'emails.*': 'email'
}

const data = {
  emails: ['[e-mail]', 'invalid.com']
}

indicative
.validate(data, rules)
.then(function () {
  // validation passed
})
.catch(function (errors) {
  // validation failed
})

Sanitizor

First rule of developing applications is to keep your datastores clean. Indicative sanitizor will help you in normalizing data by using set of specific rules.

Using Schema

Like validations you can use a schema object to sanitize our data object.

const indicative = require('indicative')

const data = {
  email: '[e-mail]',
  age: '22',
  aboutme: 'i am dev @<a href="http://nowhere.com">nowhere</a>'
}

const sanitizationRules = {
  email: 'normalize_email',
  age: 'to_int',
  aboutme: 'strip_links'
}

const sanitizedData = indicative.sanitize(data, sanitizationRules)
console.log(sanitizedData)

/**
 {
  email: '[e-mail]',
  age: 22,
  aboutme: 'i am dev @nowhere'
 }
 */

Raw Sanitizor

For quick sanitizations you can make use of raw filters

const indicative = require('indicative')
indicative.sanitizor.toInt('22') // 22
indicative.sanitizor.slug('hello world') // hello-world
indicative.sanitizor.toDate('22-1-2016') // javascript date object

Filters

Below is the list of filters available to be used for raw and schema sanitizations.

blacklist (values)

removes values inside blacklist from the actual string. Passed values are used inside a regex, so make sure to escape values properly. \\[\\] instead of \.

// raw sanitization
indicative.sanitizor.blacklist('hello world', 'ord')

// with schema
{
  description: 'blacklist:ord'
}

escape

Escapes html characters with html entities

// raw sanitization
indicative.sanitizor.escape('<div> hello world </div>')

// with schema
{
  description: 'escape'
}

normalizeEmail (options)

Normalizes email and accepts options to avoid certains transformations.

1. !lc - Do not convert email to lowercase, hence domain name will be converted to lowercase. [e-mail] will become [e-mail]

2. !rd - Stop sanitizor from removing dots.

3. !re - Do not remove everything after + symbol. [e-mail] will become [e-mail]

// raw sanitization
indicative.sanitizor.normalizeEmail('[e-mail]', ['!rd', '!re', '!lc'])

// with schema
{
  email: 'normalize_email:!rd,!re,!lc'
}

toBoolean

Converts value to a boolean, 0, false, null, undefined, '' will return false and everything else will return true.

// raw sanitization
indicative.sanitizor.toBoolean('false')

// with schema
{
  isAdmin: 'to_boolean'
}

toFloat

Converts value to float and returns NaN if unable to convert.

// raw sanitization
indicative.sanitizor.toFloat('32.55')

// with schema
{
  marks: 'to_float'
}

toInt

Converts value to integer and returns NaN if unable to convert.

// raw sanitization
indicative.sanitizor.toInt('32')

// with schema
{
  age: 'to_int'
}

toDate

Converts value to date object and returns null if unable to convert.

// raw sanitization
indicative.sanitizor.toDate('2010-22-10')

// with schema
{
  birthday: 'to_date'
}

stripLinks

Strips <a></a> tags from a given string. If input is not a string, actual value will be returned.

// raw sanitization
indicative.sanitizor.stripLinks('<a href="http://adonisjs.com"> Adonisjs </a>')

// with schema
{
  bio: 'strip_links'
}

stripTags

Strips html tags from a given string. If input is not a string, actual value will be returned.

// raw sanitization
indicative.sanitizor.stripTags('<p> Hello </p>')

// with schema
{
  tweet: 'strip_tags'
}

plural

Converts a given value to plural. Which means person will be converted to people.

// raw sanitization
indicative.sanitizor.plural('child')

// with schema
{
  november14: 'plural'
}

singular

Converts a given value to singular. Which means people will be converted to person.

// raw sanitization
indicative.sanitizor.plural('children')

// with schema
{
  november14: 'singular'
}

camelCase

Converts a given to camel-case.

// raw sanitization
indicative.sanitizor.camelCase('users-controller')

// with schema
{
  fileName: 'camel_case'
}

capitalize

capitalize a given string.

// raw sanitization
indicative.sanitizor.capitalize('doe')

// with schema
{
  fullName: 'capitalize'
}

decapitalize

decapitalize a given string.

// raw sanitization
indicative.sanitizor.decapitalize('Bar')

// with schema
{
  username: 'decapitalize'
}

title

converts a value to title case

// raw sanitization
indicative.sanitizor.title('hello-world')

// with schema
{
  title: 'title'
}

slug

Converts a value to url friendly slug.

// raw sanitization
indicative.sanitizor.slug('learn node in 30 minutes')

// with schema
{
  title: 'slug'
}

Extending

Indicative ships with a handful of validation rules, which may or may not be enough for your application that's why it is so easy to extend schema or raw validator to register your custom rules.

Extending Schema Validator

Extending Schema validator will register your custom rule to validations store and should follow defined convention, where all rules are registered as camelCase and consumed as snake_case.

For example, indicative's alpha_numeric rule is defined as alphaNumeric inside validation store.

validation method

Validation method supports async execution and should return a promise. Async execution makes is easier for you to write database driven rules. For example unique rule to check if the username already exists or not.

const unique = function (data, field, message, args, get) {

  return new Promise(function (resolve, reject) {

    // get value of field under validation
    const fieldValue = get(data, field)

    // resolve if value does not exists, value existence
    // should be taken care by required rule.
    if(!fieldValue) {
      return resolve('validation skipped')
    }

    // checking for username inside database
    User
    .where('username', fieldValue)
    .then(function (result) {
      if(result){
        reject(message)
      }else{
        resolve('username does not exists')
      }
    })
    .catch(resolve)

  })

}

Above we defined a method to check for a unique username inside the database, validation method can keep any logic to validate data but you should know about method parameters to make valid decisions.

1. data - It is the actual data object passed to validate method.
2. field - Field is a string value of field under validation.
3. message - Error message to return.
4. args - An array of values your rule is expecting, it may be empty depending upon your rule expectations. For example min:4 will have args array as [4].
5. get - it is a special function to get value for a given key from the data object, it is recommended to make use of this function as getting nested values from an object can be a tedious task and get method takes care of it.

extend

Once you have defined your validation method, you can add it to validations store by calling extend method.

indicative.extend('unique', unique, 'Field should be unique')

Extend method takes 3 required parameters to register validation to validations store.

1. name - remember to define name as camelCase which is consumed as snake_case.
2. method - validation method to be executed.
3. message - the error message to print on validation failure.

Once your custom validation rule has been stored, you can consume it inside your schema.

const rules = {
  username: 'required|unique'
}

Extending Raw Validator

Extending raw validator is fairly simple as raw validations are quick validations. An example of raw validation can be

indicative.is.email('[e-mail]')

And to extend raw validator you need to define a validation method that can accept n number of arguments based on validation expectations. A good example of raw validation can be a password strength checker

const strongPassword = function (password) {
  const strongRegex = /^(?=.*[a-z])(?=.*[A-Z])(?=.*[0-9])(?=.*[!@#\$%\^&\*])(?=.{8,})/
  return strongRegex.test(password)
}

Above we created a function to check whether a password is strong enough or not, and now we can register it is a raw validator.

indicative.is.extend('strongPassword', strongPassword)

is.extend accepts two parameters where the first one is the method name and second is validation method to execute. Finally, you can use this method as follows.

indicative.is.strongPassword('lowerUPP@123')
// returns true

Extending Sanitizor

You can also extend sanitizor to add more filters to it. All extended methods will get the value to sanitize, with an array of options.

const uppercase = function (value, options: Array) {
  return value.toUpperCase()
}

Above we created a simple method to return Uppercase version of a string. Now we will added to the list of sanitizor filters, so that we can use it later.

indicative.sanitizor.extend('uppercase', uppercase)

Now finally you can use it.

// raw sanitizor
indicative.sanitizor.uppercase('hello world')

// with schema
{
  userStatus: 'uppercase'
}

Raw Validations

Below is the list of methods supported by the raw validator, also you can extend raw validator to add your rules.

Types

Types based validations will check for a certain type

array (value)

indicative.is.array({age:22})
=> false

indicative.is.array('hello world')
=> false

indicative.is.array([20,22])
=> true

indicative.is.array([])
=> true

boolean (value)

indicative.is.boolean('true')
=> false

indicative.is.boolean('hello')
=> false

indicative.is.boolean(0)
=> true

indicative.is.boolean(1)
=> true

indicative.is.boolean(true)
=> true

indicative.is.boolean(false)
=> true

date (value [, strict])

strict true will only return true when a date object is passed.

indicative.is.date('2011-10-20')
=> true

indicative.is.date('2011-10-20', true)
=> false

indicative.is.date(new Date('2011-10-20'))
=> true

indicative.is.date(new Date('2011-10-20'), true)
=> true

function (value)

indicative.is.function(function () {})
=> true

indicative.is.function('function () {}')
=> false

null (value)

indicative.is.null(null)
=> true

indicative.is.null('null')
=> false

number (value)

indicative.is.number(22)
=> true

indicative.is.number('22')
=> false

object (value)

indicative.is.object({name:'doe'})
=> true

indicative.is.object(['doe'])
=> false

indicative.is.object('doe')
=> false

indicative.is.object({})
=> true

json (value)

indicative.is.json(JSON.stringify({name:'doe'}))
=> true

indicative.is.json(JSON.stringify([10,20]))
=> true

indicative.is.json({name:'doe'})
=> false

string (value)

indicative.is.string(JSON.stringify({name:'doe'}))
=> true

indicative.is.string('hello world')
=> true

indicative.is.string(22)
=> false

sameType (value, comparisonValue)

indicative.is.sameType(22,10)
=> true

indicative.is.sameType('hello', 'world')
=> true

indicative.is.sameType(22, '10')
=> false

Presence

existy (value)

indicative.is.existy('')
=> false

indicative.is.existy(null)
=> false

indicative.is.existy(undefined)
=> false

indicative.is.existy('hello')
=> true

indicative.is.existy(22)
=> true

truthy (value)

indicative.is.truthy(false)
=> false

indicative.is.truthy(0)
=> false

indicative.is.truthy(true)
=> true

indicative.is.truthy('hello')
=> true

falsy (value)

indicative.is.falsy(false)
=> true

indicative.is.falsy(0)
=> true

indicative.is.falsy(true)
=> false

indicative.is.falsy('hello')
=> false

empty (value)

indicative.is.empty(null)
=> true

indicative.is.empty(undefined)
=> true

indicative.is.empty({})
=> true

indicative.is.empty([])
=> true

indicative.is.empty('')
=> true

indicative.is.empty('hello')
=> false

indicative.is.empty(0)
=> false

Regex

url (value)

indicative.is.url('http://adonisjs.com')
=> true

indicative.is.url('https://adonisjs.com')
=> true

indicative.is.url('adonisjs.com')
=> false

indicative.is.url('adonisjs')
=> false

email (value)

indicative.is.email('[e-mail]')
=> true

indicative.is.url('email.org')
=> false

phone (value)

indicative.is.phone('1235554567')
=> true

indicative.is.phone('444-555-1234')
=> true

indicative.is.phone('246.555.8888')
=> true

indicative.is.phone('19929')
=> false

creditCard (value)

supports Visa,MasterCard,American Express,Diners Club,Discover,JCB

indicative.is.creditCard('4444-4444-4444-4444')
=> true

indicative.is.creditCard('4444444444444444')
=> true

indicative.is.creditCard('3685-1600-4490-1023')
=> false

alpha (value)

indicative.is.alpha('virk')
=> true

indicative.is.alpha('VIrk')
=> true

indicative.is.alpha('virk123')
=> false

alphaNumeric (value)

indicative.is.alphaNumeric('virk')
=> true

indicative.is.alphaNumeric('virk123')
=> true

indicative.is.alphaNumeric('virk@123')
=> false

ip (value)

indicative.is.ip('127.0.0.1')
=> true

indicative.is.ip('192.168.0.1')
=> true

indicative.is.ip('1:2:3:4:5:6:7:8')
=> true

indicative.is.ip('localhost')
=> false

ipv4 (value)

indicative.is.ipv4('127.0.0.1')
=> true

indicative.is.ipv4('192.168.0.1')
=> true

indicative.is.ipv4('1:2:3:4:5:6:7:8')
=> false

ipv6 (value)

indicative.is.ipv6('985.12.3.4')
=> true

indicative.is.ipv6('1:2:3:4:5:6:7:8')
=> true

indicative.is.ipv6('1.2.3')
=> false

regex (pattern, value)

run your own custom regex

indicative.is.regex(/[a-z]+/,'virk')
=> true

indicative.is.regex(/[a-z]+/,'virk123')
=> false

Arithmetic

same (value, comparisonValue)

indicative.is.same(10,5+5)
=> true

indicative.is.same('hello','hello')
=> true

indicative.is.same('10',10)
=> false

even (value)

indicative.is.even(10)
=> true

indicative.is.even(5)
=> false

odd (value)

indicative.is.odd(10)
=> false

indicative.is.odd(5)
=> true

positive (value)

indicative.is.positive(10)
=> true

indicative.is.positive(-10)
=> false

negative (value)

indicative.is.negative(10)
=> false

indicative.is.negative(-10)
=> true

above (value, comparisonValue)

indicative.is.above(10, 20)
=> false

indicative.is.above(30,20)
=> true

under (value, comparisonValue)

indicative.is.under(30, 20)
=> false

indicative.is.under(10,20)
=> true

between (value, min, max)

indicative.is.between(20,10,30)
=> true

indicative.is.between(5,10,30)
=> false

Array

inArray (value, comparsionArray)

indicative.is.inArray(10,[10,20,40])
=> true

indicative.is.inArray(5,[10,20,40])
=> false

sorted (value)

indicative.is.sorted([10,20,40,50])
=> true

indicative.is.sorted([10,15,5,20])
=> false

intersectAny (value, comparisonArray)

indicative.is.intersectAny([10,20],[30,10,40])
=> true

indicative.is.intersectAny([10,20],[30,50,40])
=> false

intersectAll (value, intersectAll)

indicative.is.intersectAll([10,20],[20,10,50,40])
=> true

indicative.is.intersectAll([10,20],[10,50,40])
=> false

Dates

today (value)

indicative.is.today(new Date())
=> true

// if today date is 2015-11-30
indicative.is.today("2015-11-30")
=> true

const yesterday = new Date(new Date().setDate(new Date().getDate() - 1))
indicative.is.today(yesterday)
=> false

yesterday (value)

indicative.is.yesterday(new Date())
=> false

// if yesterday date was 2015-11-29
indicative.is.yesterday("2015-11-29")
=> true

const yesterday = new Date(new Date().setDate(new Date().getDate() - 1))
indicative.is.yesterday(yesterday)
=> true

tomorrow (value)

indicative.is.tomorrow(new Date())
=> false

// if tomorrow date will be 2015-12-01
indicative.is.tomorrow("2015-12-01")
=> true

const tomorrow = new Date(new Date().setDate(new Date().getDate() + 1))
indicative.is.tomorrow(tomorrow)
=> true

past (value)

indicative.is.past("2001-01-10")
=> true

const tomorrow = new Date(new Date().setDate(new Date().getDate() + 1))
indicative.is.past(tomorrow)
=> false

future (value)

indicative.is.future("2001-01-10")
=> false

const tomorrow = new Date(new Date().setDate(new Date().getDate() + 1))
indicative.is.future(tomorrow)
=> true

after (value, afterDate)

indicative.is.after("2015-10-01", "2015-10-03")
=> false

indicative.is.after("2015-10-01", "2015-09-10")
=> true

before (value, beforeDate)

indicative.is.before("2015-10-01", "2015-10-03")
=> true

indicative.is.before("2015-10-01", "2015-09-10")
=> false

dateFormat (value, formats)

indicative.is.dateFormat("2015-10-01", ['YYYY-MM-DD'])
=> true

indicative.is.dateFormat("2015/10/01", ['YYYY-MM-DD'])
=> false

indicative.is.dateFormat("2015/10/01", ['YYYY-MM-DD', 'YYYY/MM/DD'])
=> true

inDateRange (value, minDate, maxDate)

indicative.is.inDateRange("2015-10-01", "2015-09-01", "2015-12-01")
=> true

indicative.is.inDateRange("2015-10-01", "2015-11-01", "2015-12-01")
=> false

Schema Rules

Schema rules can/may be different from raw validation rules. In order make use of schema validation rules you need to pass a schema object to indicative validate or validateAll method.

const indicative = require('indicative')

const rules = {
  username : 'required|alpha_numeric|min:6|max:20',
  email    : 'required|email'
}

indicative
.validate(data, rules)
.then (function () {
  // validation passed
})
.catch(function () {
  // validation failed
})

above accepted after after_offset_of alpha alpha_numeric array before before_offset_of boolean date date_format different email ends_with equals in includes integer ip ipv4 ipv6 json max min not_equals not_in object range regex required required_if required_when required_with_all required_with_any required_without_all required_without_any same starts_with string under url

above

the field under validation should be above defined value

{
  age : 'above:18'
}

accepted

field should have been accepted with truthy value for ex - yes,1,true

{
  toc: 'accepted'
}

after

the value of field should be after define date

{
  newyear_party: 'after:2015-12-24'
}

after_offset_of

the value of field should be after defined offset from today's date

{
  expires: 'after_offset_of:12,months'
}

alpha

the value of field should contain letters only

{
  name: 'alpha'
}

alpha_numeric

the value of field should contain letters and numbers only

{
  username: 'alpha_numeric'
}

array

the value should be an array

{
  permissions : 'array'
}

before

the value of field should be before define date

{
  file_tax: 'before:2015-03-31'
}

before_offset_of

the value of field should be before defined offset from today's date

{
  enrollment: 'before_offset_of:1,year'
}

boolean

value of field should contain a boolean value, true,false,0,1,'0','1' will yield true

{
  is_admin: 'boolean'
}

date

the value of field should be a valid date, MM/DD/YYYY, MM-DD-YYYY, YYYY-MM-DD, YYYY/MM/DD formats are allowed

{
  published_on: 'date'
}

date_format

the value of field should be a valid date according to given format

{
  published_on: 'date_format:YYYY-MM-DD'
}

different

the value of 2 fields should be different

{
  alternate_email: 'different:email'
}

email

should be a valid email address

{
  email_address: 'email'
}

ends_with

the string should end with given letters

{
  domain: 'ends_with:.com'
}

equals

the value of field under validation should equal the defined value

{
  age: 'equals:26'
}

in

the value of field should fall within defined values

{
  gender: 'in:Male,Female,Other'
}

includes

the value of field should include define letters

{
  sub_domain: 'includes:adonisjs'
}

integer

the value of field under validation should be an integer

{
  age: 'integer'
}

ip

the value of field under validation should be a valid ip address

{
  ip_address: 'ip'
}

ipv4

the value of field under validation should be a valid ipv4 address

{
  ip_address: 'ipv4'
}

ipv6

the value of field under validation should be a valid ipv6 address

{
  ip_address: 'ipv6'
}

json

value of field is safe for JSON.parse

{
  meta_data: 'json'
}

max

The length of a given field should not be more than defined length. Numbers and strings are evaluated same way.

{
  password: 'max:20'
}

min

The length of a given field should not be less than defined length. Numbers and strings are evaluated same way

{
  password: 'min:6'
}

not_equals

the value of field under should be different from defined value

{
  username: 'not_equals:admin'
}

not_in

the value of field under should not be one of the defined values.

{
  username: 'not_in:admin,super,root'
}

object

the value of field should be a valid javascript object

{
  profile: 'object'
}

range (alias:between)

value of field should be inside defined range, shorthand for min and max

{
  password: 'range:6,20'
}

regex

the value of field under validation should satisfy regex pattern.

Note : Always define rules as array when making use of regex rule

{
  username: ['regex:^[a-zA-z]+$']
}

required

the field should exist and contain some value

{
  username: 'required'
}

required_if

the field is required when defined field exists

{
  password_confirmation: 'required_if:password'
}

required_when

the field is required when value of defined field is same as defined value

{
  state: 'required_when:country,US'
}

required_with_all

the field is required when all other fields are present

{
  social_geek: 'required_with_all:twitter,facebook,tumblr'
}

required_with_any

the field is required when any of the other fields are present

{
  social_login: 'required_with_any:facebook_token,twitter_token'
}

required_without_all

the field is required when all of the other fields does not exist

{
  rent: 'required_without_all:onwer,buyer'
}

required_without_any

the field is required when any of the other fields does not exist

{
  sell: 'required_without_any:onwer,buyer'
}

same

the value of field should be same as the value of define field

{
  password_confirm: 'same:password'
}

starts_with

the value of field should start with defined letters

{
  accepted: 'starts_with:y'
}

string

the value of field under validation should be a string

{
  username: 'string'
}

under

the value of field should be under defined value

{
  age: 'under:60'
}

url

the value of field should be a valid url

{
  blog: 'url'
}