Validate JSON objects against a schema written in JSON
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  • Small, light, zero dependencies.
  • Can be used in Node, browsers, and Mongo/Couch Map/Reduce functions.
  • Offers an error object similar to ActiveRecord validations.
  • Can be used declaratively as well as immediately.
  • Good test coverage.


var inRange = Valid.min(4).max(9) inRange(12) // throws an error var stringInRange = inRange.typeof('string').errorHandler(Valid.TrueFalse) if(stringInRange.validate("not in range")) { /* not executed */ }


var check = Valid.checker(TrueFalse); // uses Throw by default if(check(12).inRange(4,9)) { /* not executed */ }

what about going insane?

Object.prototype.assert = Valid.checker().errorHandler(Valid.Throw); 12.assert().min(4).max(9); // throws an error

Handling Validation Errors

By default the validator raises an error when it finds invalid data (using the Valid.Throw handler). To make it return a boolean result:





ErrorObject (included with json-valid)

errors: an error object .add([field], msg) -- adds a message for the field. A field of "." refers to the entire object. .clear() -- clears all error messages .count([field]) -- tells how many total errors or just for the given field .messages([field]) -- returns an array of all error messages concated with field name

Built-In Validations

Don't include validations by default? Syntax is very personal. Do you prefer in, contains, isIn, etc? Don't do isBlah. Just blah. Find the BARE MINIMUM non-composed validators. Users can compose their own APIs.

in(1,2) equivalent: in([1,2]) in({1:ignored,2:ignored}) in is a keyword... use synonym isIn if this is a problem. have a synonym module? Valid.isOneOf =

match(regex) length(min, [max]) applies to strings, arrays, or any object that has a length field.

and(Validation, Validation, ...) though why would you do this since Validation.validation().validation() is the same. or(Validation, Validation, ...) not(Validation) Make any a synonym for or and every a synonym or and? What about not(and) and not(or)? optional(Validation, Validation, ...) min -- uses JS's < and > operators so can be used on strings too. max -- also gt, ge, lt, le, eq, ne?

isDate isBefore isAfter

isEmail() isIP() isUrl() isUUID()

json(template) -- checks an entire json structure

We don't offer inverses because not() is usually clearer. If you'd rather write Valid.notIn(arr) instead of Valid.not(, just do this:

Valid.notIn = function(arr) { return Valid.not( } Valid.notIn = Valid.not( // could this work?

Extending Valid


Error Handlers

// this.field tells what field we're operating on Valid.errorHandler(function(message) {


  • Only supports immediate use, can't declare validations.
  • The syntax is pretty sweet: check('abc').len(6,12).isEmail();
  • only meant to work inside node?

  • Only supports static validation, can't do quick immediate validations.
  • Doesn't support static schemas (must use {\__.eq(12)} instead of {12}).
  • Produces unsatisfying error messages on deeply nested schemas.


Pain-free MIT.