Aval

A minimalist functional validation library. Inspired by joi, React PropTypes and Angular form validation.

Aval is a lightweight library to help validate JS data and is aimed at helping form validation feedback.

Why?

There are a LOT of JavaScript data validators, however here are a few facts about Aval:

• has a nice compact syntax
• validates data and outputs a detailled validation report containing only boolean values
• doesn't throw errors or output localised validation messages
• allows to define custom validators
• can validate nested properties

Installation

It is available on npm and bower:

$ npm install --save aval
$ bower install --save aval

It is available in commonJs format, AMD and global (bundled and uglified).

Usage

Get a new instance of Aval and chain validators. Calling validate(val) will output an object containing a valid boolean and a key-value pairs object errors.

import Aval from 'aval';
 
let validator = Aval().string().required().min(3);
 
let report = validator.validate(null);
// Will output
report = {
    valid: false,
    errors: {
        string:   false,
        required: false
    }
}
 
 
let report = validator.validate('hi')
// Will output
report = {
    valid: false,
    errors: {
        string:   false,
        required: false,
        min:      true
    }
}
 
 
report = validator.validate('hello')
// Will output
report = {
    valid: true,
    errors: {
        string:   false,
        required: false,
        min:      false
    }
}
 

Validators

• For all type validators, null or undefined values won't fail. required() will fail them if present.

• For all other validators, a non-existing value will cause the validator to return null, excluding it from the errors report.

• Types

  • string()
  • number()
  • boolean()
  • object()
  • array()
  • date()
  • set()

• Range assertions (numbers and dates)

  • lt(max): lower than
  • lte(max): lower than or equal
  • gt(min): greater than
  • gte(min): greater than or equal

• Discrete range assertions (any)

  • inList(arr): in array or Set
  • notInList(arr): not in array or Set

• Values

  • required(): required value (null, undefined, empty array, empty object, empty string will all fail)
  • pattern(regex): pattern matching
  • exactly(val): reference equality (any)
  • withElm(elm): includes an element (array or Set)
  • withoutElm(elm): excludes an element (array or Set)

• Length assertions (strings, arrays and objects)

  • min(min): minimum length (strings or arrays)
  • max(max): maximum length (strings or arrays)
  • minKeys(min): minimum number of keys (objects)
  • maxKeys(max): maximum number of keys (objects)

• Nested

  • prop(name, validator): property validation
  • every(validator): all elements validation (collection: array or Set)

Custom validator

You can define custom validators. A validator can take a number of arguments, all non-optional, the last being the value to validate.

import Aval, {addValidator} from 'aval'
 
addValidator('matchPwd', function (val) {
    if (!val) return null;
    return val.password === val.password2;
});
 
let data = {
    username: 'troch',
    email: null,
    password:  'm4g1cPWD'
    password2: 'm4g1cPWd'
};
 
let validator = Aval().object().required().matchPwd();
 
let report = validator.validate(data)
// Will output
report = {
    valid: false,
    errors: {
        object:   false,
        required: false,
        matchPwd: true
    }
}

Nested properties

You can validate nested properties (as deep as you want).

import Aval from 'aval'
 
let data = {
    username: 'troch',
    email: null,
    password:  'm4g1cPWD'
    password2: 'm4g1cPWd'
}
 
let validator = Aval().object().required().matchPwd()
    .prop('username', Aval().string().required().min(4))
    .prop('email',    Aval().string().required().pattern(/^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$/))
    .prop('password', Aval().string().required().min(5));
 
let report = validator.validate(data)
// Will output
report = {
    valid: false,
    errors: {
        object:   false,
        required: false,
        matchPwd: true
    },
    props: {
        username: {
            valid: true,
            errors: {
                string:   false,
                required: false,
                min:      false
            }
        },
        email: {
            valid: false,
            errors: {
                string:   false,
                required: true
            }
        },
        password: {
            valid: true,
            errors: {
                string:   false,
                required: false,
                min:      false
            }
        }
    }
}

Collections

You can apply the every\ validator on all elements of an array, allowing you to easily validate collections. Only one every validator per property is allowed.

import Aval, {addValidator} from 'aval'
 
// Let's create a custom validator for even numbers
addValidator('even', val => {
    // if (val === null || val === undefined) return null;
    return val % 2 === 0;
})
 
// Let's validate this array
let evenNumbers = [2, 4, 6, 7]
 
// Validator (minimum 2 numbers, all even)
let validator = Aval()
    .array().required().min(2)
    .every(Aval().number().even())
 
let report = validator.validate(evenNumbers)
// Will output
report = {
    valid: false,
    errors: {
        array:    false,
        required: false,
        min:      false,
        every:    true
    },
    elements: [
        {
            valid: true,
            errors: {number: false, even: false}
        },
        {
            valid: true,
            errors: {number: false, even: false}
        },
        {
            valid: true,
            errors: {number: false, even: false}
        },
        {
            valid: false,
            errors: {number: false, even: true}
        }
    ]
}