Quick reference for `checkit` validators

This article was originally published at https://gist.github.com/joepie91/cd107b3a566264b28a3494689d73e589 . 
 Presence 
 
 exists - The field must exist, and not be undefined . 
 required - The field must exist, and not be undefined , null or an empty string. 
 empty - The field must be some kind of "empty". Things that are considered "empty" are as follows:
 
 "" (empty string) 
 [] (empty array) 
 {} (empty object) 
 Other falsey values 
 
 
 
 Character set 
 
 alpha - a-z , A-Z 
 alphaNumeric - a-z , A-Z , 0-9 
 alphaUnderscore - a-z , A-Z , 0-9 , _ 
 alphaDash - a-z , A-Z , 0-9 , _ , - 
 
 Value 
 Length-related validators may apply to both strings and arrays. 
 
 exactLength: length - The value must have a length of exactly length . 
 minLength: length - The value must have a length of at least length . 
 maxLength: length - The value must have a length of at most length . 
 contains: needle - The value must contain the specified needle (applies to both strings and arrays). 
 accepted - Must be a value that indicates agreement - varies by language (defaulting to en ):
 
 en, fr, nl - "yes" , "on" , "1" , 1 , "true" , true 
 es - "yes" , "on" , "1" , 1 , "true" , true , "si" 
 ru - "yes" , "on" , "1" , 1 , "true" , true , "да" 
 
 
 
 Value (numbers) 
 Note that "numbers" refers to both Number-type values, and strings containing numeric values! 
 
 numeric - Must be a finite numeric value of some sort. 
 integer - Must be an integer value (either positive or negative). 
 natural - Must be a natural number (ie. an integer value of 0 or higher). 
 naturalNonZero - Must be a natural number, but higher than 0 (ie. an integer value of 1 or higher). 
 between: min : max - The value must numerically be between the min and max values (exclusive). 
 range: min : max - The value must numerically be within the min and max values (inclusive). 
 lessThan: maxValue - The value must numerically be less than the specified maxValue (exclusive). 
 lessThanEqualTo: maxValue - The value must numerically be less than or equal to the specified maxValue (inclusive). 
 greaterThan: minValue - The value must numerically be greater than the specified minValue (exclusive). 
 greaterThanEqualTo: minValue - The value must numerically be greater than or equal to the specified minValue (inclusive). 
 
 Relations to other fields 
 
 matchesField: field - The value in this field must equal the value in the specified other field . 
 different: field - The value in this field must not equal the value in the specified other field . 
 
 JavaScript types 
 
 NaN - Must be NaN . 
 null - Must be null 
 string - Must be a String . 
 number - Must be a Number . 
 array - Must be an Array . 
 plainObject - Must be a plain object (ie. object literal). 
 date - Must be a Date object. 
 function - Must be a Function . 
 regExp - Must be a RegExp object. 
 arguments - Must be an arguments object. 
 
 Format 
 
 email - Must be a validly formatted e-mail address. 
 luhn - Must be a validly formatted creditcard number (according to a Luhn regular expression). 
 url - Must be a validly formatted URL. 
 ipv4 - Must be a validly formatted IPv4 address. 
 ipv6 - Must be a validly formatted IPv6 address. 
 uuid - Must be a validly formatted UUID. 
 base64 - Must be a validly formatted base64 string.