Validate objects against predefined rules (node.js).

npm install rules
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rules (node.js)

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Small declarative rules framework designed primarily for use when validating incoming data, such as JSON coming into services.


You create an object to declare the rules/invariants you want to apply (something akin to a schema). A fluent interface makes it easy to specify the invariants for each property:

var nameRules = {
    first  : mustBe().populated().string({ minLength: 5, maxLength: 20}),
    second : mustBe().populated().string({ minLength: 5, maxLength: 20}),

var personRules = {
    name:        nameRules,
    weight:      mustBe().populated().numeric({min : 0, max: 130}),
    dateOfBirth: mustBe().date({ before: now.subtract("years", 1) })

You can also do inline validation:

var doSomeStuff = function(name, age) {
    ensure(age, "age").integer();
# This schema is not showing how to validate a real address, its just an example that makes it easy to test the framework
addressRules = {
  streetOne: mustBe().populated()
  streetTwo: -> @.populated().string( minLength: 10, maxLength : 50 ) [2]
  streetThree: -> @.populated().string( minLength : 10, maxLength: 50) 
  town: -> @.populated()
  postCode: -> @.populated().matchFor(/.../)

As shown you can access this fluent interface using twp approaces:

  • [1] mustBe() - Acts as the entry point to the fluent interface.
  • [2] function - 'this' inside the function being the entry point to the fluent interface.
Triggering validation

You trigger validation using:

result = rules.apply(person, personRules)

The returned object has the per-property details of any validation failures, e.g.:

    name: { 
        first: { 
            message: 'The value must be populated.',
            type: 'not_populated',
            value: '' 
        second: { 
            message: 'The value must be populated.',
            type: 'not_populated',
            value: undefined } 
    weight: { 
        message: 'The value must be populated.',
        type: 'not_populated',
        value: undefined 

Note in this case both the first name (e.g. and second name ( needed to be populated, along with the weight.


The project comes with examples in the examples directory:

node examples/person
coffee examples/address

Note that if you are using sublime you can get the alignment shown in the person example using the sublime text alignment package.


The framework comes with several validators, to understand them further you may want to run the examples.

  • populated - Checks the value is not null, undefined, "", or an empty array.
  • array
  • numeric - Optionally you can also pass in object with min and/or max values
  • matchFor - You can pass in an object with pattern and optionally flags, alternatively you can pass in the RegExp object to use.
  • date - Optionally you can specify that the date must be before and/or after specified dates. To make this easier you use now.add or now.subtract to specify the dates to use for before/after.
  • string - Optionally you can pass in minLength and/or maxLength.


First install mocha:

npm install mocha -g

Run the tests using npm test or:

mocha -R spec spec/ -w -G --recursive -b


  • Numeric validators - >, <, >=, <=
  • Date validator - Support now()
  • boolean validator
  • enum style validator - valueIn(list), valueNotIn(list).
  • Potentially UMD support
  • Trying to apply multiple of same validator, multiple type validators (integer and string, numeric and boolean), regex with anything other than string
  • Ensure interface e.g. ensure(5).populate().numeric(), allowing direct validation of single values
  • API for throwing
  • Cyclical rules objects warning
  • Numeric validator - failing if passed "15.5"
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