valdat

A modern-day validator for the masses, designed for ease of use. Its design is influenced by prop-type and Joi. Although, not as exhaustive as Joi.

Let's explore an React example first:

class User extends React.Component {
    state = {
        name: '',
        nameMessage: '',
        sex: '',
        sexMessage: '',
        age: '',
        ageMessage: '',
        languages: [],
        languagesMessage: '',
        preference: {},
        preferenceMessage: ''
    }

    onSubmit = () => {

        // create data object
        const {
            name,
            sex,
            age,
            languages,
            preference
        } = this.state;
        const data = {
            name,
            sex,
            age,
            languages,
            preference
        };

        // create schema object
        const schema = {
            name: valdat.string().isRequired(),
            sex: valdat.oneOf(['Male', 'Female', 'Other']),
            age: valdat.number().min(18).isRequired(),
            languages: valdat.array().notEmpty().ofType(valdat.string()),
            preference: valdat.object().shape({
                email: valdat.boolean().isRequired(),
                theme: valdat.string().isRequired()
            }).isRequired()
        };

        // check if data matches schema
        const {
            isValid,
            errors
        } = valdat.check(schema, data);

        // reduce the error messages and update error messages
        // this can also clear existing error messages
        const errorMsgs = Object.keys(errors)
            .reduce((msgs, key) => ({
                ...msgs,
                [`${key}Message`]: errors[key]
            }), {});
        this.setState({ ...errorMsgs });

        // if the data is okay
        if (isValid) {
            // call api to submit
        }
    }
}

That wasn't so bad was it? A similar flow can also be create for any of the popular frameworks.

Features

1. Ability to curry (chain) multiple assertions
2. Assertions fail-fast, meaning it will stop checking if one of them fails
3. Returned errors object has the same shape as schema, with/without an error message. Very easy to update UI without much hassle
4. Ability to add custom validator
5. Ability to register custom assertions
6. Sufficient list of assertions (still growing)

Fail-fast

All the Validate<Type> classes extends a Validate base class that provides the following:

• stack: an array into to which the curried assertion functions are pushed
• required: a boolean which will be set true if the isRequired() curry is called
• isRequired(): if the assertion should expect a value

When we call valdat.check(schema, data), each item of schema is an instance of Validate<Type> class, meaning it has its own this.stack. valdat.check will loop through this stack and break as soon as an assertion fails. The assertion function always returns an object with { error: boolean, message: string }, thus allowing us to do nested assertions, for eg: valdat.array().ofType(valdat.string()) or valdat.oneOfType([valdat.string(), valdat.number()])

Installation

npm install valdat --save

Usage

---

import valdat from 'valdat';

// to create custom assertion class
import valdat { Validate } from 'valdat';

// for typescript
import valdat, {
    Validate,
    IValidate,
    IValidator
} from 'valdat';

API - utility methods

check

Check the data against the schema. It will return an object with isValid: boolean and errors: <SchemaShape>{}.

const {
    isValid,
    errors
} = valdat.check(schema, data);

custom

Use a totally custom assertion function. There is not isRequired() in this case. It must be implemented within the custom assertion.

const schema = {
    password: valdat.custom((data, key) => {
        const regex = /^[\w&.-]+$/;
        const value = data[key];
        let error = false;
        let message = '';

        if (!regex.test(value)) {
            error = true;
            message = 'Should contain: minimum 8 letters, upper & lower letters, numbers, and special characters';
        }

        // Important for assertion to work
        return {
            error,
            message
        }
    }),
}

register

Imagine you reach a stage where your custom assertion requires its own currying, or it needs to be reused accross the application. Then you can create a new Validate<Type> class by extending the base Validate class and register to valdat object literal. After that you can use your custom assertion anywhere.

import valdat, { Validate } from 'valdat';

class ValidateCat extends Validate {
    constructor() {
        super();
    }
    cat() {
        this.stack.push((data, key) => {
            const value = data[key]

            if (!value || !value.cat) {
                return {
                    error: true,
                    message: `${key} in data is not a cat.`
                }
            }

            // Important for assertion to work
            return {
                error: false,
                message: ''
            }
        });

        // Important for currying
        return this;
    }
    isLazy() {
        this.stack.push((data, key) => {
            const value = data[key]

            if (value && !value.isLazy) {
                return {
                    error: true,
                    message: 'The cat is not lazy.'
                }
            }

            return {
                error: false,
                message: ''
            }
        });

        // Important for currying
        return this;
    }
};

valdat.register('cat', () => new CatValidation().cat());

const schema = {
    prickle: valdat.cat().isLazy().isRequired()
};

API - assertion methods

Each of the following methods are from their own Validate<Type> classes, which extends the base class Validate, which provides .isRequired(). The following assertion methods returns this, allowing us to curry through the additional methods. The methods are included in valdat object literal for correct sequential access. Register API does the same thing.

string

Checks if the value of the key in data is a string.

const schema = {
    name: valdat.string().isRequired()
};

string.hasLen

Checks if this string has a length of 5.

const schema = {
    name: valdat.string().hasLen(5)
};

string.matchRegex

Checks if this string matches the provided regex.

const schema = {
    name: valdat.string().matchRegex(/^Solo$/)
};

number

Checks if the value of the key in data is a number.

const schema = {
    age: valdat.number().isRequired()
};

number.min

Checks if this number has a minimum value of 18.

const schema = {
    age: valdat.number().min(18)
};

number.max

Checks if this number has a maximum value of 30.

const schema = {
    age: valdat.number().max(30)
};

boolean

Checks if the value of the key in data is a boolean.

const schema = {
    publicAccess: valdat.boolean().isRequired()
};

object

Checks if the value of the key in data is an object.

const schema = {
    preference: valdat.object().isRequired()
};

object.shape

Checks if this object has the exact shape as provided.

const schema = {
    preference: valdat.object().shape({
        email: valdat.boolean().isRequired(),
        theme: valdat.string().isRequired()
    })
};

array

Checks if the value of the key in data is an array.

const schema = {
    languages: valdat.array().isRequired()
};

array.notEmpty

Checks if this array is not empty.

const schema = {
    languages: valdat.array().notEmpty()
};

array.ofType

Checks if each item in this array contains the specified type.

const schema = {
    languages: valdat.array().ofType(valdat.string())
};

oneOf (enum)

Checks if the value of the key in data exactly matches one the provided enums values

const schema = {
    sex: valdat.oneOf(['Male', 'Female', 'Other'])
};

oneOfType (enum)

Checks if the value of the key in data exactly matches one the provided enums types

const schema = {
    nationality: valdat.oneOfType([
        valdat.string(),
        valdat.array()
    ])
};