node-validator is a library of string validation, filtering and sanitization methods.

To install node-validator, use npm:

$ npm install validator

To use the library in the browser, include validator-min.js

Example

var check = require('validator').check,
    sanitize = require('validator').sanitize
    
//Validate
check('[email protected]').len(6, 64).isEmail();       //Methods are chainable
check('abc').isInt();                               //Throws 'Invalid integer'
check('abc', 'Please enter a number').isInt();      //Throws 'Please enter a number'
check('abcdefghijklmnopzrtsuvqxyz').is(/^[a-z]+$/);

//Sanitize / Filter
var int = sanitize('0123').toInt();                  //123
var bool = sanitize('true').toBoolean();             //true
var str = sanitize(' \s\t\r hello \n').trim();      //'hello'
var str = sanitize('aaaaaaaaab').ltrim('a');        //'b'
var str = sanitize(large_input_str).xss();
var str = sanitize('&lt;a&gt;').entityDecode();     //'<a>'

Web development

Often it's more desirable to check or automatically sanitize parameters by name (rather than the actual string). See this gist for instructions on binding the library to the request prototype.

Example http://localhost:8080/?zip=12345&foo=1&textarea=large_string

get('/', function (req, res) {
    req.onValidationError(function() {
        //Redirect the user..
    });
    
    //Validate user input
    req.check('zip', 'Please enter a valid ZIP code').len(4,5).isInt();
    req.check('email', 'Please enter a valid email').len(6,64).isEmail();
    req.checkHeader('referer').contains('localhost');
    
    //Sanitize user input
    req.sanitize('textarea').xss();
    req.sanitize('foo').toBoolean();
    
    //etc.
});

List of validation methods

is()                            //Alias for regex()
not()                           //Alias for notRegex()
isEmail()
isUrl()                         //Accepts http, https, ftp
isIP()
isAlpha()
isAlphanumeric()
isNumeric()                     
isInt()                         //isNumeric accepts zero padded numbers, e.g. '001', isInt doesn't
isLowercase()
isUppercase()
isDecimal()
isFloat()                       //Alias for isDecimal
notNull()
isNull()
notEmpty()                      //i.e. not just whitespace
equals(equals)
contains(str)
notContains(str)
regex(pattern, modifiers)       //Usage: regex(/[a-z]/i) or regex('[a-z]','i')
notRegex(pattern, modifiers)
len(min, max)                   //max is optional

List of sanitization / filter methods

trim(chars)                     //Trim optional `chars`, default is to trim whitespace (\r\n\t\s)
ltrim(chars)                    
rtrim(chars)                    
ifNull(replace)
toFloat()
toInt()
toBoolean()		                //True unless str = '0', 'false', or str.length == 0
toBooleanStrict()	            //False unless str = '1' or 'true'
entityDecode()                  //Decode HTML entities
entityEncode()
xss()                           //Remove common XSS attack vectors from text (default)
xss(true)                       //Remove common XSS attack vectors from images

Extending the library

When adding to the Validator prototype, use this.str to access the string and this.error(this.msg || default_msg) when the string is invalid

var Validator = require('validator').Validator;
Validator.prototype.contains = function(str) {
    if (!~this.str.indexOf(str)) {
        this.error(this.msg || this.str + ' does not contain ' + str);
    }
    return this; //Allow method chaining
}

When adding to the Filter (sanitize) prototype, use this.str to access the string and this.modify(new_str) to update it

var Filter = require('filter').Filter;
Filter.prototype.removeNumbers = function() {
    this.modify(this.str.replace(/[0-9]+/g, ''));
    return this.str;
}

Error handling

By default, the validation methods throw an exception when a check fails

try {
    check('abc').notNull().isInt()
} catch (e) {
    console.log(e); //Invalid integer
}

To set a custom error message, set the second param of check()

try {
    check('abc', 'Please enter a valid integer').notNull().isInt()
} catch (e) {
    console.log(e); //Please enter a valid integer
}

To attach a custom error handler, set the error method of the validator instance

var Validator = require('validator').Validator;
var v = new Validator();
v.error = function(msg) {
    console.log('Fail');
}
v.check('abc').isInt(); //'Fail'