not-valid

Composable message-based validation

Installation

$ npm install not-valid --save

Usage

Overview

import { validate } from "not-valid";

// Use createValidator to specify a rule and the message given for breaking that rule
const mustContainA = createValidator<string>(v => v.indexOf("A") !== -1, "Value must contain the letter 'a'");

// pass in array of validation functions and a value to validate
validate([ mustContainA ], "cheese"); // [ "Value must contain the letter 'a'" ] - returns error messages

// can use a factory pattern for your validation methods to make things nice
const mustContain = (requirement: any) => {
    return createValidator<string | Array<any>>(v => v.indexOf(requirement) !== -1, `Value must contain '${requirement}'`);
};

const lengthWithinBounds = (min: number, max: number) => {
    return createValidator<string>(v => v.length < min || v.length > max, `Value must have length between ${min} and ${max}`);
};

// you can pass in multiple validators
validate([ 
    mustContain("Z"), 
    lengthWithinBounds(2, 6)
], "Too long a string, they say!"); // [ "Value must contain 'Z'", "Value must have length between 2 and 6" ]

Validators

A number of validation functions come bundled with this package. You can use them like so:

import { validators } from "not-valid";

validate([
    validators.validLength({ min: 6, max: 12 })
], "Good value");

The validators included are as follows:

• requiredString
• requiredNumber
• validLength
• validEmail
• validAlphaNumeric
• validOption
• validPhoneNumber
• validNINumber
• validUKDrivingLicence
• validSortCode
• validBankAccountNumber
• validVATNumber

Creating validation functions

A validation function must take in a value value, and return Result.Pass if value is valid, or Result.Fail(message) is value is invalid. They can also return Result.Stop, which will silently stop the validation cycle (no more errors).

This can be done with the helper method createValidator in not-valid:

import { createValidator } from "not-valid";

const mustContainA = createValidator<string>(v => v.indexOf("A") !== -1, "Value must contain the letter 'a'");

You can use factory patterns around this to make it nicer:

const mustContain = (requirement: any) => {
    return createValidator<string | Array<any>>(v => v.indexOf(requirement) !== -1, `Value must contain '${requirement}'`);
};

All validators (except for validators that explicitly check for "required") should treat empty string, null and undefined as valid. This is because we can combine validators with "required" validators in order to enforce something being valid and not empty, but also allows us to accept nothing being entered if desired.

Options

The third parameter of validate is an object containing options.

interface ValidationOptions {
    sequential?: boolean;
}

sequential

Default: true

The validation will break on the first error, therefore only returning a single validation error.

validate([ something, another ], 5, { sequential: false });

If something fails validation, another will not be called.

License

Made with 💖 by NewOrbit in Oxfordshire, and licensed under the MIT Licence