Awesome

property-validator

:white_check_mark: Easy property validation for JavaScript, Node and Express

Built on top of validator.js, property-validator makes validating request parameters easy and fun. No chaining, no prototype violations, no magic. Just some simple, stateless, javascript functions.

All you have to do is import some base validation functions and declare the validation rules for your request.

Table of contents

• Installation
• Usage
• Usage in NodeJS
  • Request Validation
    • Request Parameters
    • Query String
    • Body
    • Headers
    • Everything
    • Assert Middleware
• Advanced usage
  • Optional Validation
  • Custom Error Messages
  • Custom localization
  • Custom Validation Functions
• Validation Helpers
  • Supported Helpers
  • Not currently supported
• Usage with TypeScript
• Contributing
• License

Installation

npm install --save property-validator

Usage

property-validator provides a suite of validate and assert functions to make request validation simple and easy to write.

assert functions halt the programs's execution if one of the validation rules breaks.

import { assert, presence, email } from 'property-validator';

let user = {
  username: 'nettofarah',
  email_address: 'invalid@email'
}

assert(user, [
  presence('username'),
  email('email_address')
]);

// will throw a ValidationError

// /Users/netto/projects/property-validator/lib/request_assertions.js:8
//    throw new ValidationError(validation);

validate functions on the other hand, will return an object containing the result of all validations.

import { validate, presence, email } from 'property-validator';

let user = {
  username: 'nettofarah',
  email_address: 'invalid@email'
}

validate(user, [
  presence('username'),
  email('email_address')
]);

// returns
{
  valid: false,
  errors :[
    {
      field: "email_address",
      message: "\"email_address\" should look like an email address"
    }
  ],
  messages: [
    "\"email_address\" should look like an email address"
  ]
}

property-validator really shines when you combine it with web servers.

Usage in NodeJS

You can run validations and assertions against the request body, query, params and headers, or against all of them at once using assertAll or validateAll.

Using assertAll:

import express from 'express';
import { assertAll, presence, email, assertMiddleware } from 'property-validator';

const app = express();

app.get('/hello', function(req, res){
  assertAll(req, [
    presence('username'),
    email('email_address')
  ]);

  res.status(200).json({ name: req.query.username });
});

app.use(assertMiddleware);

Request Validation

property-validator offers out of the box support for request params, query string, body and header validations.

All you have to do is to import the correct function and annotate your request handler.

Request Parameters

You can run validations against incoming request params.

import { validateParams, presence } from 'property-validator';

app.get('/hello/:username', function(req, res){
  const validation = validateParams(req, [
    presence('username')
  ]);

  if (validation.valid) {
    res.status(200).json({ name: req.query.username });
  } else {
    res.status(422).json({ errors: validation.errors });
  }
});

or use the assertParams counterpart:

import { assertParams, presence } from 'property-validator';

app.get('/hello/:username', function(req, res){
  assertParams(req, [
    presence('username')
  ]);

  // No need to check the validation result
  res.status(200).json({ name: req.query.username });
});

Query String

import { validateQuery, email } from 'property-validator';

app.get('/hi', function(req, res){
  const validation = validateQuery(req, [
    email('primary_email_address')
  ]);

  if (validation.valid) {
    res.status(200).send('We promise not to send spam!');
  } else {
    res.status(422).json({ errors: validation.errors });
  }
});

or use the assertQuery counterpart:

import { assertQuery, email } from 'property-validator';

app.get('/hi', function(req, res){
  assertQuery(req, [
    email('primary_email_address')
  ]);

  // No need to check the validation result
  res.status(200).send('We promise not to send spam!');
});

Body

import { validateBody, presence, email } from 'property-validator';

app.post('/sign-up', function(req, res){
  const validation = validateBody(req, [
    email('user.email'),
    presence('user.password'),
    presence('user.password_confirmation')
  ]);

  if (validation.valid) {
    res.status(200).send('Welcome!');
  } else {
    res.status(422).send({ errors: validation.errors });
  }
});

or use the assertBody counterpart:

import { assertBody, presence, email } from 'property-validator';

app.post('/sign-up', function(req, res){
  assertBody(req, [
    email('user.email'),
    presence('user.password'),
    presence('user.password_confirmation')
  ]);

  // No need to check the validation result
  res.status(200).send('Welcome!');
});

Headers

import { validateHeaders, presence, format } from 'property-validator';

app.get('/secret-stuff', function(req, res){
  const validation = validateHeaders(req, [
    presence('Authorization'),
    format('Authorization', /Token token="\w+"/)
  ]);

  if (validation.valid) {
    res.status(200).send('Here is all your secret stuff!');
  } else {
    res.status(401).send('You shall not pass!');
  }
});

or use the assertHeaders counterpart:

import { assertHeaders, presence, format } from 'property-validator';

app.get('/secret-stuff', function(req, res){
  assertHeaders(req, [
    presence('Authorization'),
    format('Authorization', /Token token="\w+"/)
  ]);

  // No need to check the validation result
  res.status(200).send('Here is all your secret stuff!');
});

Everything

You can use validateAll or assertAll to run validation rules against all properties at once (body, params, query). Important: validateAll and assertAll will not run validations agains headers since they're pretty different use cases.

Assert Middleware

property-validator ships with a standard middleware that automatically handles assert errors. All you have to do is to import assertMiddleware and mount it after all request handlers in your express app.

import express from 'express';
import { assertAll, presence, email, assertMiddleware } from 'property-validator';

const app = express();

app.get('/hello', function(req, res){
  assertAll(req, [
    presence('username'),
    email('email_address')
  ]);

  res.status(200).json({ name: req.query.username });
});

app.post('/bla', ...);
...

app.get('/test', ...);

app.use(assertMiddleware);

You can also roll your own middleware in case you need any sort of customization.

import { ValidationError } from 'property-validator';

app.use(function(err, req, res, next) {
  // Do not swallow all kinds of errors
  const isValidationError = (err instanceof ValidationError);
  if (!isValidationError) {
    return next(err);
  }

  const messages = err.messages;
  res.status(422);

  res.json({
    notice: "Your request is invalid",
    errors: messages
  })
});

Advanced usage

property-validator is extensible. You can set optional property validation, customize your custom messages and write your own validation functions.

Optional Validation

optional is a special validation helper that can be used when fields are not strictly required, but need to be validated in case they are present.

You can pass in any other validation helper, and propery-validator will only run the helper function against the input params if the optional field is present.

Pagination is usually a good use case for optional params:

var validation = validate(params, [
  optional(isNumeric('limit')),
  optional(isNumeric('offset'))
]);

Custom Error Messages

Validation helpers allow custom messages to be set. You can set the validation message to any string you want.

All you need to do is to pass in a custom error message as the last param when calling any validation helper.

var validation = validate(params, [
  presence('name', 'Oops, you forgot to tell us your name'),
  isCurrency('rent_in_brl', { symbol: 'R$' }, 'Reais should be prefixed with R$'),
  isCurrency('rent', 'This does not look like money')
]);

It is also possible to use some of the parameters of your validator in the error message.

var validation = validate(params, [
  presence('name', 'Oops, you forgot to tell us your :paramName'),
  isLength('value', { min: 10, max: 99 }, 'The :paramName should be between :min and :max')
]);

//Oops, you forgot to tell us your name
//The value should be between 10 and 99

Custom localization

It is possible to override the default locals. The locals is a simple object with keys refering to a validation function and there value the message.

import { assert, presence, isLength, email, setLocals } from 'property-validator';
setLocals({
  required: 'Oops, you forgot to tell us your :paramName'
});

var validation = validate(params, [
  presence('name'),
  isLength('value', { min: 10, max: 99 }, 'The :paramName should be between :min and :max'),
  email('email')
]);

//Oops, you forgot to tell us your name
//The value should be between 10 and 99
//"email" should look like an email address

As you can see all kind of combinations are possible. You can override the default locals and still set a custom message. And if you neither supply a translation through the setLocals nor set a custom message, it will fall back to the default locals.

If you would like to restore the locals to the default locals simply call restoreDefaultLocals like so:

import { restoreDefaultLocals } from 'property-validator';

restoreDefaultLocals();

Custom Validation Functions

Writing your own validation functions is easy.

// Your function will receive a property name as its argument
function isTheUltimateAnswer(propertyName) {
  // and then return a function that takes the
  // actual object you want to validate
  return function(subject) {
    var value = subject[propertyName]
    var isAnswer = value === 42

    // Make sure your function returns `result`, `message`
    // and `field`
    return {
      result: isAnswer,
      message: value + " is not the Answer to the Ultimate Question of Life, The Universe, and Everything",
      field: propertyName
    }
  }
}

You can now use your custom function as you would with any other validation helper:

var subject = {
  'guess': 43
}

var validation = validate(subject, [
  isTheUltimateAnswer('guess')
]);

Validation Helpers

Validation helpers are functions you can use to validate incoming request properties.

property-validator relies on the super battle tested validator.js library.

Supported Helpers

Here's a list of currently supported helpers:

Not currently supported

These are a few other helpers avaliable in validator.js that could be used in property-validator. Feel free to submit a PR if you need any of these functions.

Usage with TypeScript

There is no need to install additional type definitions for property-validator since it ships with TypeScript definition files.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/nettofarah/property-validator. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Code of Conduct.

To run the specs check out the repo and follow these steps:

$ npm install
$ npm run test

License

The module is available as open source under the terms of the MIT License.