A promise-based validation engine for Node.js.

Usage no npm install needed!

<script type="module">
  import validationEngine from '';



This is a validation engine for Node.js. It is not intended to have every possible validation rule in the core, but it is built in such a way that you can easily add external rules.

The main advantage of this module is that you can asynchronously validate every rule of your Model at once: = function(data){
      //save people data
      //some validation rule was not satisfied

It is my first module, so contributions and hints are very welcome!



  npm install validation-engine

Configuring Validation Rules for a Model

You can use directly the rules property of the validator object:

  var validator = require('validator-engine');
  validator.rules = [
      'field' : 'email',
      'rules' : [
          //these parameters are passed to the validator function as arguments
          'rule' : 'maxLength',
          'length' : 255,
          'message' : 'Maximum of 255 characters'
        //you can run database queries asynchronously
      'field' : 'email_confirmation',
      'rules' : [{
        'rule' : 'equal',
        'fieldToCompare' : 'email'

obs: Check the core validators here.

Adding Custom Validators

It is very simple to add custom validators:

  var Promise = require('bluebird');

  validator.addValidator('equal', function(rule, field_name, data){
    return new Promise(function(resolve, reject){
      if (data[field_name] === data[rule.fieldToCompare]) return resolve();
      return reject(new validator.ValidatorException('error message', field_name, rule, data));

You can even extend the module object with all of your validation rules at once. At lib/myValidator.js. put

  var validator = require('validator-engine');
  //add your validators
  module.exports = validator;

So, at your model, you can use

  var validator = require('../lib/myValidator');

Conditional Validation

You may choose to check certain validation rules only when inserting or updating data, using the on option in the rule

  validator.rules = [
      'field' : 'email',
      'rules' : [{
        'rule' : 'required',
        'on' : 'create'

The accepted values for on are create and update. The module checks if the current operation is create or update looking for the primary option.

If data[validator.primary] is present, the operation is update; otherwise, it is create. The default value for primary is id, but you can change it to any value you need.

  validator.primary = 'email';

Core validators

There are some validators in the core. All the core validators accept undefined values, except, of course, required. They all have default error messages, but you are encouraged to customize them. To do it, use the message parameter.

  • length validate the string.length property. Parameters:
    • length (optional) if set, string.length must match its value;
    • minLength (optional) if set, string.length must be greater or equal to its value;
    • maxLength (optional) if set, string.length must be less or equal to its value;

You can combine minLength and maxLength in the same rule, in such a way that string.length must be between minLength (inclusive) and maxLenght (inclusive).

  • required check if typeof data[field_name] is not undefined.
  • alphanumeric - check if the field has only letters and numbers. Optionally, this rule may accept whitespaces and underscores too. Parameters:
    • whitespace (default : false) if true, whitespaces are allowed.
    • underscore (default : false) if tre, underscores are allowed.
  • regExp check if the field match a regular expression. Parameters:
    • reg_exp (required) - regular expression which the field should match.