@modulify/validator

This library provides a declarative validation utility.

The utility does not include text messages in the generated violations but instead provides metadata that can be used to create a custom view for them.

Installation

Using yarn:

yarn add @modulify/validator

or, using npm:

npm install @modulify/validator --save

Usage

import {
  HasLength,
  HasProperties,
  IsDefined,
  IsString,
  validate,
} from '@modulify/validator'

const violations = await validate({
  form: {
    nickname: '',
    password: '',
  },
}, HasProperties({
  form: [
    IsDefined(),
    HasProperties({
      nickname: IsString.That(HasLength({ min: 4 })),
      password: IsString.That(HasLength({ min: 6 })),
    }),
  ],
})) /* [{
  by: '@modulify/validator/IsString',
  value: '',
  path: ['form', 'nickname'],
  reason: 'min',
  meta: 4,
}, {
  by: '@modulify/validator/IsString',
  value: '',
  path: ['form', 'password'],
  reason: 'min',
  meta: 6,
}] */

or (for synchronous validation):

const violations = validate.sync({
  form: {
    nickname: '',
    password: '',
  },
}, HasProperties({
  form: [
    IsDefined(),
    HasProperties({
      nickname: IsString.That(HasLength({ min: 4 })),
      password: IsString.That(HasLength({ min: 6 })),
    }),
  ],
}))

Exported types

• Violation – an object that contains information about a value – why it violates one or more constraints; includes following fields:
  • value – value that violates something;
  • path – path to the value, an empty array for scalar values and represents full path to the value in a complex object;
  • violates – indicator of the violated constraint;
  • reason – indicator of the reason why the constraint is violated;
  • meta – some data to describe the reason – what exactly the boundaries were not met;

  import type { Violation } from '@modulify/validator/types'

• Predicate – function that accepts a value and returns true or false; logical unit that is used for checking multiple things: type or if the value satisfies certain criteria; accepts generic argument T to specify the type of the value, if predicate returns true;

  import type { Predicate } from '@modulify/validator/types'

• Assertion – extension of the Predicate type that includes:
  • fqn – field – some predefined name that will be used as a value for the violates field of Violation;
  • bail – field – flag that interrupts further validation if the assertion fails;
  • reason – field, optional – string or symbol that is used to indicate, why assertion has failed; always added to a violation object, if present;
  • meta – field, optional – some metadata to use in further analysis; always added to a violation object, if present;
  • That – method – used to extend assertion with other assertions;
  • also – field – readonly array of other assertions that was attached by That method;

  import type { Assertion } from '@modulify/validator/types'

Exported members

• validate – function that accepts a value for validation as the first argument, constraints as the second, and path to a value as the third (that is optional and used mostly for internal purposes, as validation is recursive); includes method sync that has the same arguments set but performs validation synchronously and throws error when finds an asynchronous constraint;

• Assert – creates assertion from logical predicate:

  const IsSomething = Assert(isSomething, {
    fqn: 'Some fqn',
    bail: true,
  })

  Arguments:

  • Logical predicate
  • Options, that includes fqn, bail, reason (optional), and meta (optional);

• HasLength – checks length property of the specified string or array; can be configured with options:

  • exact – if the length should be exactly equal the specified value;
  • max – if the length should be equal or less than the specified value;
  • min – if the length should be equal or greater than the specified value;
  • bail – set this to true if you need to interrupt further validation if the assertion fails;

• IsBoolean – checks if the value is boolean; interrupts further validation if fails;

• IsDate – checks if the value is Date object; interrupts further validation if fails;

• IsDefined – checks if the value is not undefined; interrupts further validation if fails;

• IsEmail – checks if the value is a valid email; interrupts further validation if fails;

• IsNull – checks if the value is null; interrupts further validation if fails;

• IsNumber – checks if the value is number; interrupts further validation if fails;

• IsString – checks if the value is string; interrupts further validation if fails;

• IsSymbol – checks if the value is a symbol; interrupts further validation if fails;

• OneOf – checks if the value equal to one of the specified values; can be configured with:

  • equalTo – predicate f(a, b) that checks if two values are equal or not; by default the strict === comparison is used
  • bail – set this to true if you need to interrupt further validation if the assertion fails;

• Each – a runner that runs validation for each element in array;

• HasProperties – a runner that runs object's structure check.