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An express.js middleware for node-validator.


npm install express-validator


var util = require('util'),
    bodyParser = require('body-parser'),
    express = require('express'),
    expressValidator = require('express-validator'),
    app = express();
app.use(bodyParser.bodyParser({ extended: true }));
app.use(expressValidator([options])); // this line must be immediately after any of the bodyParser middlewares!'/:urlparam', function(req, res) {
  // checkBody only checks req.body; none of the other req parameters 
  // Similarly checkParams only checks in req.params (URL params) and 
  // checkQuery only checks req.query (GET params). 
  req.checkBody('postparam', 'Invalid postparam').notEmpty().isInt();
  req.checkParams('urlparam', 'Invalid urlparam').isAlpha();
  req.checkQuery('getparam', 'Invalid getparam').isInt();
  // OR assert can be used to check on all 3 types of params. 
  // req.assert('postparam', 'Invalid postparam').notEmpty().isInt(); 
  // req.assert('urlparam', 'Invalid urlparam').isAlpha(); 
  // req.assert('getparam', 'Invalid getparam').isInt(); 
  // as with validation these will only validate the corresponding 
  // request object 
  // OR find the relevent param in all areas 
  // Alternatively use `var result = yield req.getValidationResult();` 
  // when using generators e.g. with co-express 
  req.getValidationResult().then(function(result) {
    if (!result.isEmpty()) {
      res.status(400).send('There have been validation errors: ' + util.inspect(result.array()));
      urlparam: req.params.urlparam,
      getparam: req.query.getparam,
      postparam: req.body.postparam

Which will result in:

$ curl -d 'postparam=1' http://localhost:8888/test?getparam=1

$ curl -d 'postparam=1' http://localhost:8888/t1est?getparam=1
There have been validation errors: [
  { param: 'urlparam', msg: 'Invalid urlparam', value: 't1est' } ]

$ curl -d 'postparam=1' http://localhost:8888/t1est?getparam=1ab
There have been validation errors: [
  { param: 'getparam', msg: 'Invalid getparam', value: '1ab' },
  { param: 'urlparam', msg: 'Invalid urlparam', value: 't1est' } ]

$ curl http://localhost:8888/test?getparam=1&postparam=1
There have been validation errors: [
  { param: 'postparam', msg: 'Invalid postparam', value: undefined} ]

Middleware Options



The errorFormatter option can be used to specify a function that must build the error objects used in the validation result returned by req.getValidationResult().
It should return an Object that has param, msg, and value keys defined.

// In this example, the formParam value is going to get morphed into form body format useful for printing. 
  errorFormatter: function(param, msg, value) {
      var namespace = param.split('.')
      , root    = namespace.shift()
      , formParam = root;
    while(namespace.length) {
      formParam += '[' + namespace.shift() + ']';
    return {
      param : formParam,
      msg   : msg,
      value : value


{ "validatorName": function(value, [additional arguments]), ... }

The customValidators option can be used to add additional validation methods as needed. This option should be an Object defining the validator names and associated validation functions.

Define your custom validators:

 customValidators: {
    isArray: function(value) {
        return Array.isArray(value);
    gte: function(param, num) {
        return param >= num;

Use them with their validator name:

req.checkBody('users', 'Users must be an array').isArray();
req.checkQuery('time', 'Time must be an integer great than or equal to 5').isInt().gte(5)


{ "sanitizerName": function(value, [additional arguments]), ... }

The customSanitizers option can be used to add additional sanitizers methods as needed. This option should be an Object defining the sanitizer names and associated functions.

Define your custom sanitizers:

 customSanitizers: {
    toSanitizeSomehow: function(value) {
        var newValue = value;//some operations 
        return newValue;

Use them with their sanitizer name:




   req.check('testparam', 'Error Message').notEmpty().isInt();
   req.check('testparam.child', 'Error Message').isInt(); // find nested params 
   req.check(['testparam', 'child'], 'Error Message').isInt(); // find nested params 

Starts the validation of the specifed parameter, will look for the parameter in req in the order params, query, body, then validate, you can use 'dot-notation' or an array to access nested values.

If a validator takes in params, you would call it like req.assert('reqParam').contains('thisString');.

Validators are appended and can be chained. See chriso/validator.js for available validators, or add your own.


Alias for req.check().


Alias for req.check().


Same as req.check(), but only looks in req.body.


Same as req.check(), but only looks in req.query.


Same as req.check(), but only looks in req.params.


Only checks req.headers. This method is not covered by the general req.check().


Only checks req.cookies. This method is not covered by the general req.check().

Validation by Schema

Alternatively you can define all your validations at once using a simple schema. Schema validation will be used if you pass an object to any of the validator methods.

You may pass per-validator error messages with the errorMessage key. Validator options may be passed via options key as an array when various values are needed, or as a single non-null value otherwise.

 'email': {
    optional: {
      options: { checkFalsy: true } // or: [{ checkFalsy: true }] 
    isEmail: {
      errorMessage: 'Invalid Email'
  'password': {
    notEmpty: true,
    matches: {
      options: ['example', 'i'] // pass options to the validator with the options property as an array 
      // options: [/example/i] // matches also accepts the full expression in the first parameter 
    errorMessage: 'Invalid Password' // Error message for the parameter 
  'name.first': { // 
    optional: true, // won't validate if field is empty 
    isLength: {
      options: [{ min: 2, max: 10 }],
      errorMessage: 'Must be between 2 and 10 chars long' // Error message for the validator, takes precedent over parameter message 
    errorMessage: 'Invalid First Name'

You can also define a specific location to validate against in the schema by adding in parameter as shown below:

 'email': {
    in: 'query',
    notEmpty: true,
    isEmail: {
      errorMessage: 'Invalid Email'

Please remember that the in attribute will have always highest priority. This mean if you use in: 'query' then checkQuery() will be called inside even if you do checkParams() or checkBody(). For example, all of these calls will check query params for email param:

var schema = {
 'email': {
    in: 'query',
    notEmpty: true,
    isEmail: {
      errorMessage: 'Invalid Email'
  'password': {
    notEmpty: true,
    matches: {
      options: ['example', 'i'] // pass options to the validator with the options property as an array 
      // options: [/example/i] // matches also accepts the full expression in the first parameter 
    errorMessage: 'Invalid Password' // Error message for the parameter 
req.check(schema);        // will check 'password' no matter where it is but 'email' in query params 
req.checkQuery(schema);   // will check 'password' and 'email' in query params 
req.checkBody(schema);    // will check 'password' in body but 'email' in query params 
req.checkParams(schema);  // will check 'password' in path params but 'email' in query params 
req.checkHeaders(schema);  // will check 'password' in headers but 'email' in query params 

Currently supported location are 'body', 'params', 'query', 'headers'. If you provide a location parameter that is not supported, the validation process for current parameter will be skipped.

Validation result

Result API

The method req.getValidationResult() returns a Promise which resolves to a result object.

req.assert('email', 'required').notEmpty();
req.assert('email', 'valid email required').isEmail();
req.assert('password', '6 to 20 characters required').len(6, 20);
req.getValidationResult().then(function(result) {
  // do something with the validation result 

The API for the result object is the following:


Returns a boolean determining whether there were errors or not.


Sets the firstErrorOnly flag of this result object, which modifies the way other methods like result.array() and result.mapped() work.

This method is chainable, so the following is OK:



Returns an array of errors.
All errors for all validated parameters will be included, unless you specify that you want only the first error of each param by invoking result.useFirstErrorOnly().

var errors = result.array();
// errors will now contain something like this: 
  {param: "email", msg: "required", value: "<received input>"},
  {param: "email", msg: "valid email required", value: "<received input>"},
  {param: "password", msg: "6 to 20 characters required", value: "<received input>"}


Returns an object of errors, where the key is the parameter name, and the value is an error object as returned by the error formatter.

Because of historical reasons, by default this method will return the last error of each parameter.
You can change this behavior by invoking result.useFirstErrorOnly(), so the first error is returned instead.

var errors = result.mapped();
// errors will now be similar to this: 
  email: {
    param: "email",
    msg: "valid email required",
    value: "<received input>"
  password: {
    param: "password",
    msg: "6 to 20 characters required",
    value: "<received input>"


If there are errors, throws an Error object which is decorated with the same API as the validation result object.
Useful for dealing with the validation errors in the catch block of a try..catch or promise.

try {
} catch (e) {
  res.send('oops, validation failed!');

Deprecated API

The following methods are deprecated.
While they work, their API is unflexible and sometimes return weird results if compared to the bleeding edge req.getValidationResult().

Additionally, these methods may be removed in a future version.


Returns synchronous errors in the form of an array, or an object that maps parameter to error in case mapped is passed as true.
If there are no errors, the returned value is false.

var errors = req.validationErrors();
if (errors) {
  // do something with the errors 


Returns a promise that will either resolve if no validation errors happened, or reject with an errors array/mapping object. For reference on this, see req.validationErrors().

req.asyncValidationErrors().then(function() {
  // all good here 
}, function(errors) {
  // damn, validation errors! 

String formatting for error messages

Error messages can be customized to include both the value provided by the user, as well as the value of any parameters passed to the validation function, using a standard string replacement format:

%0 is replaced with user input %1 is replaced with the first parameter to the validator %2 is replaced with the second parameter to the validator etc...


req.assert('number', '%0 is not an integer').isInt();
req.assert('number', '%0 is not divisible by %1').isDivisibleBy(5);

Note: string replacement does not work with the .withMessage() syntax. If you'd like to have per-validator error messages with string formatting, please use the Validation by Schema method instead.

Per-validation messages

You can provide an error message for a single validation with .withMessage(). This can be chained with the rest of your validation, and if you don't use it for one of the validations then it will fall back to the default.

req.assert('email', 'Invalid email')
    .notEmpty().withMessage('Email is required')


  {param: 'email', msg: 'Email is required', value: '<received input>'}
  {param: 'email', msg: 'Invalid Email', value: '<received input>'}

Optional input

You can use the optional() method to skip validation. By default, it only skips validation if the key does not exist on the request object. If you want to skip validation based on the property being falsy (null, undefined, etc), you can pass in { checkFalsy: true }.

//if there is no error, is either undefined or a valid mail. 



req.body.comment = 'a <span>comment</span>';
req.body.username = '   a user    ';
req.sanitize('comment').escape(); // returns 'a &lt;span&gt;comment&lt;/span&gt;' 
req.sanitize('username').trim(); // returns 'a user' 
console.log(req.body.comment); // 'a &lt;span&gt;comment&lt;/span&gt;' 
console.log(req.body.username); // 'a user' 

Sanitizes the specified parameter (using 'dot-notation' or array), the parameter will be updated to the sanitized result. Cannot be chained, and will return the result. See chriso/validator.js for available sanitizers, or add your own.

If a sanitizer takes in params, you would call it like req.sanitize('reqParam').whitelist(['a', 'b', 'c']);.

If the parameter is present in multiple places with the same name e.g. req.params.comment & req.query.comment, they will all be sanitized.


Alias for req.sanitize().


Same as req.sanitize(), but only looks in req.body.


Same as req.sanitize(), but only looks in req.query.


Same as req.sanitize(), but only looks in req.params.


Only sanitizes req.headers. This method is not covered by the general req.sanitize().


Only sanitizes req.cookies. This method is not covered by the general req.sanitize().

Regex routes

Express allows you to define regex routes like:

app.get(/\/test(\d+)/, function() {});

You can validate the extracted matches like this:

req.assert(0, 'Not a three-digit integer.').len(3, 3).isInt();


If you have been using this library with TypeScript, you must have been using the type definitions from DefinitelyTyped.

However, as of v3.1.0, the type definitions are shipped with the library. So please uninstall the typings from DT. Otherwise they may cause conflicts


Check the GitHub Releases page.


Copyright (c) 2010 Chris O'Hara, MIT License