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A lightweight, chaining validation library.

  • Zero dependencies. Can be used in browsers, Node, and Mongo/Couch Map/Reduce functions.
  • Recursively tests JSON data structures.
  • Easy to extend with your own validations.
  • Excellent test coverage (run npm test).
    var Valid = require('valid');
    var inRange = Valid.number().min(4).max(9)
    inRange.check(3)            // check returns true/false, here it returns false
    inRange.test(12)            // returns "is not less than or equal to 9"

    Valid.optional().string().check(null);       // can be null, undefined, or a string
    Valid.array(Valid.integer).check([1,2,3]);   // checks each item in the array
    var isHex = Valid.match(/^[0-9A-F]$/i).message("should be a hexadecimal number");

    // test JSON structures:
    var Schema = {
        Name:     Valid.notBlank(),
        Address: {
            State:    /^[A-Z][A-Z]$/,  // shortcut for Valid.match(/^[A-Z][A-Z]$/)
            Country:  "US"

    var data = {
        Name:     "Jed",
        Numbers:  [1, 9, 25],
        Address: {
            State:    "CA",
            Country:  "US"


    // Easily define your own validations:
    Valid.isPowerOfTen = Valid.mod(10).message("should be a power of ten).define();


This library is scary new.

  • covert to Rails-like "5 should equal 4" instead of current "5 is not equal to 4"?
  • simplify error objects
  • try to shrink the api, implement kitchen-sink
  • npm publish
  • pass a json schema to array()? factor into RunSubtest & have everything call this.
  • write isDate, isBefore, isAfter
  • write isEmail() isIP() isUrl() isUUID()
  • test coverage?
  • Allow putting value first? i.e. Valid(9).lt(12).gt(10) throws "9 is not greater than 10"
  • write an assertion function? Valid.assert(12).integer().min(5);
  • convert to using nested functions instead of the __queue array?
  • do a doctest somehow


Valid allows you to declare a validation and then test it against any number of values:

    var validation = Valid.integer().even().min(6);
    validation.check(9);      // returns "9 is not even"
    validation.isValid(10);   // returns true.

check() returns undefined if the validation succeeds, a string like "should not be null" if it fails, or an error object for JSON validations (see Errors below). isValid() just returns true or false.

Built-In Validations

This is probably incomplete. See valid.js.

  • Presence: defined(), undef(), undefined*(), nil(), null*(), notNull()
  • Equality: equal(a[,b...]), notEqual(...), oneOf(arrayOrObject), in*(arrayOrObject)
  • Comparison: eq(n), lt(n), le(n), ge(n), gt(n), ne(n)
  • Numbers: number(), integer(), mod(x[,rem]), even(), odd()
  • Booleans: boolean(), isTrue(), true*(), isFalse(), false*()
  • Arrays: array([validationForEachItem]), len(min,max), empty()
  • Strings: string(), len(min,max), blank(), notBlank()
  • Regexps: match(regex[,modifiers]), nomatch(regex[,modifiers])
  • Logic: and(test[,test...]), or(test[,test...]), not(test,message)
  • Utilities: nop(), fail([message]), message(msg), todo([test])
  • JSON: json(schema)

*: These are JavaScript keywords. While Valid.undefined() works with a lot of interpreters, it doesn't work everywhere. Each keyword validation has a more compatible alternative that should be used instead: Valid.undef(), Valid.nil(), etc.


When a validation fails, the validation returns a string ready for concatenation: "is not even", "is not equal to 12", "mod 4 is 2". If the error is being thrown then the failing value is tacked onto the front: "3 is not even", "null is not equal to 12", "6 mod 4 is 2".

There is one exception: JSON validations. Because they can return multiple errors, they return an object instead of a string. The value field contains the value that failed to validate.

        "Name"               : { message: "is blank", value: "" },
        "Addresses[0].State" : { message: "doesn't match /[A-Z][A-Z]/", value: "ca" }

Extending Valid

To define your own validations, just end the chain with "define()" and add it to the root object:

    Valid.latitude  =;
    Valid.longitude =;
    Valid.integer().latitude().isValid(20);  // true!

You can also add validations that take parameters:

    Valid.mod10 = function(rem) { return this.mod(10,rem) }
    Valid.mod10(6).check(127);   // returns "127 mod 10 is 7 not 6"

Or just rename them:

    Valid.every = Valid.and;
    Valid.any = Valid.or;


On Node 0.4.x, if the console tries to print a Valid chain, you get this error:

> Valid.integer()
TypeError: Function.prototype.toString is not generic
    at Function.toString (native)
    at Array.toString (native)

It's a Node bug. 0.5.x does the correct thing and prints the chain:

> Valid.integer()
{ _queue: 
   [ { [Function: SimpleTest] data: [Object] },
     { [Function: SimpleTest] data: [Object] } ] }


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

  • Validates JSON using a declared schema.
  • Only supports static use, can't do immediate validations.
  • Produces unsatisfying error messages on deeply nested schemas.


Pain-free MIT.

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