@valkyriestudios/validator

An extensible javascript validator

npm install @valkyriestudios/validator

Example usage

import Validator from '@valkyriestudios/validator';

const v = new Validator({
    first_name: 'required|string|min:2',
    last_name: 'required|string|min:2',
    password: 'required|string|min:8',
    confirmation: 'required|equal_to:<password>',
    gender: '?in:<meta.genders>',
    age: '?integer|between:0,150',
});

const evaluation = v.validate({
    first_name: 'Peter',
    last_name: 'Vermeulen',
    password: 'mySecr3tPass',
    confirmation: 'mySecr3tPass',
    gender: 'm',
    meta: {
        genders: ['m','f','o']
    };
});

console.log(evaluation.is_valid); // true

How does this work?

Instantiating a new validator

A validator instance is reusable across multiple validation runs, it's instantiated with a set of rules that it needs to validate later down the line. These rules can go from single dimensional kv objects to multi-dimensional kv objects.

You can create very small validators ... = new Validator({ email: 'required|string|email' }); to very complex validators using a simple readable syntax.

...new Validator({
    address: {
        street: 'required|string|alpha_num_spaces',
        nr: 'required|integer',
        zip: 'required|integer|between:1000,9999',
    },
    contact: {
        email: 'required|string|email',
    }
});

Anatomy of a validation descriptor

Validation of a value can be a simple one-off thing, or it can be a set of rules that the value needs to go through, as such a validation descriptor can contain multiple rules.

The syntax for this is best shown with a good example required|integer|between:1000,9999.

• |
  The | symbol is a delimiter to show where a new rule starts

• :
  The : symbol marks where the rule name ends and the parameter list for the rule starts

• ,
  The , symbol marks where a new parameter starts

As such the example rule here validates on 3 things, the required rule, integer rule and between rule, where the between rule has 2 parameters (1000, 9999).

Running validations and checking evaluations

After a validator instance is created, you can run it as many times as you want to validate a data object passed to it. The resultset of this is called an evaluation and is returned when calling the validate function.

const evaluation = myvalidator.validate({ name: 'Peter', age: '250' });

The evaluation object consists of two keys that can be used to determine the result of the validation:

• is_valid
  A boolean value that tells you whether or not the validation succeeded (true) or not (false)

• errors
  An object containing the errors per validated key, each key in the ruleset will be represented here, if a key was correctly validated it will be an empty array, otherwise it will be an array containing the specific rules that didn't match.

example of an evaluation object:

{
    is_valid: false,
    errors: {
        name: [],
        age: [
            {msg: 'integer', params: []},
            {msg: 'between', params: ['1','150']}
        ],
    },
}

Revisiting evaluations

The validator instance will remember and internally store the last evaluation, you can always link back to it through the is_valid property and the errors property on the validator instance.

Linking to other parameters inside of the data object

Validation sometimes requires context, this context is usually linked to other variables in the data object that is being validated. Think of a password confirmation that needs to be matched, or a string that needs to be in a provided string of arrays. For this we've added the ability to parameterize your ruleset.

Parameterization happens through the following syntax <myparam> where myparam is the key of the value it needs to link to in the data object.

Example of a parameterized equal to rule:

const v = new Validator({ a: 'equal_to:<meta.b>' });

v.validate({ a: 'hello', b: 'world' }); // is_valid = false
v.validate({ a: 'foo', b: 'foo' }); // is_valid = true

Example of a parameterized greater_than rule:

const v = new Validator({ a: 'greater_than:<meta.b>' });

v.validate({ a: 50, b: 40 }); // is_valid = true
v.validate({ a: 10, b: 20 }); // is_valid = false

Take note: Custom rules (see below) do not need any special definition for this to work.

Optional rules

In some cases you only want to validate a specific key if it is passed, if not you don't want to run the validations. To allow for this we've added the ? flag.

To make use of the ? flag, place it at the very start of the defined rule.

Example of an optional rule:

const v = new Validator({ gender: '?string|in:<meta.genders>'});

v.validate({ genders: ['m', 'f', 'o']}); // is_valid = true
v.validate({ gender: 'X', genders: ['m', 'f', 'o']}); // is_valid = false

Extending the validator with custom rules

A validator library can/should only provide the default rules that would cover 90% of the validation use cases, however some validations are custom to your specific case, as such you can add your own custom rules through the extend static function on the Validator class.

Adding a rule to the Validator is global and shared among all other validator instances, so it's advised to do this at boot.

Example of a rule that will validate whether a string is a user role:

Validator.extend('user_role', function (val) {
    return ['admin', 'user', 'guest'].includes(val);
});

example usage
(new Validator({ a: 'user_role' })).validate({ a: 'owner' }); // is_valid = false
(new Validator({ a: 'user_role' })).validate({ a: 'admin' }); // is_valid = true

Example of a rule that will validate whether an integer is the double of a provided parameter

Validator.extend('is_double', function (val, param) {
    return val === (param * 2);
});

example usage
const v = (new Validator({
    a: 'is_double:<meta.b>'
}));

v.validate({ a: 6, meta: { b: 4 }}); // is_valid = false
v.validate({ a: 8, meta: { b: 4 }}); // is_valid = true

Available rules

The following list shows you all the default rules that are provided by this library, feel free to write your own or open a PR to extend on this set!

Rule	Description
alpha_num_spaces	Validate a string to only contain alphabetical, numerical and space characters
alpha_num_spaces_multiline	Ditto alpha_num_spaces but with the addition of allowing linebreak and carriage returns
array	Validate that a provided value is an array
between	Validate that a provided value is between two numbers, if passed a string or array this will validate on length
boolean	Validate that a provided value is a boolean
color_hex	Validate that a provided value is a hex color (with the # included)
date	Validate that a provided value is a date object
email	Validate that a provided value is an email, take note: this only structurally tests if an email is good, it doesn't test whether an email actually exists
equal_to	Validate that a provided value is equal to another value, this can be used on primitives (string, number, boolean) but also on non-primitives (objects, arrays, dates). Equality checks for non-primitives are done through FNV1A hashing
greater_than	Validate that a provided value is greater than a provided number, if passed a string or array this will validate on length
greater_than_or_equal	Validate that a provided value is greater than or equal than a provided number, if passed a string or array this will
validate on length
in	Validate that a provided value is in a set of values, this requires parameterization (see above)
integer	Validate that a provided value is an integer, this will see NaN as invalid
less_than	Validate that a provided value is less than a provided number, if passed a string or array this will validate on length
less_than_or_equal	Validate that a provided value is less than or equal to a provided number, if passed a string or array this will validate on length
max	Alias of less_than_or_equal
min	Alias of greater_than_or_equal
number	Validate that a provided value is a number, this will see NaN as invalid
object	Validate that a provided value is an object, arrays will not be seen as objects by this rule
required	Validate that a provided value is not empty, arrays will be seen as valid if at least 1 element is present, strings will be seen as empty if when trimmed the length is bigger than 0, null and undefined will not be valid and a NaN will also be rejected
size	Validate that a provided value has a specific size, this only applies to strings and arrays and checks on length
string	Validate that a provided value is a string
url	Validate that a provided value is a url, this allows for query string values as well
url_noquery	Validate that a provided value is a url without any query string values

Contributors

• Peter Vermeulen : Valkyrie Studios