inspected

Simple JavaScript object validation

inspected is a small library for validating JavaScript objects against schemas, inspired by the API of spected.

Getting Started

Install inspected:

npm i inspected

yarn add inspected

Define a schema:

import isRequired from 'inspected/schema/is-required'
import isOptional from 'inspected/schema/is-optional'
import isFunction from 'inspected/schema/is-function'
import isString from 'inspected/schema/is-string'

const schema = {
  name: [[isRequired(isString), 'Name is required.']],
  process: [[isOptional(isFunction), 'Process is an optional function.']],
}

Note that inspected comes with a number of useful functions for building schemas in the schema folder, or you can define any predicate to validate object properties. See the spected documentation for more information.

Validate an object instance against the schema:

import validate from 'inspected/validate'

const validator = validate(schema)

validator({
  name: 'foo',
  process: () => {},
})
//=> { isValid: true, errors: { property: {}, object: {} } }

validator({
  foo: 'bar',
})
//=> { isValid: false, errors: { property: { name: ['Name is required.'], foo: ['Unexpected property.'] }, object: {} } }

Validation result:

Property	Description
`isValid`	True if the object satisfies the schema and object rules, false otherwise.
`errors`	Object containing any `property` errors and `object` rule errors.

Validate an object instance against object rules

The validate function also supports an optional rules parameter. This allows the validation of rules which aren't associated with an individual property, but rather rules that affect the entire object instance.

For example:

const schema = {
  forename: [[isRequired(isString), 'Forename is required.']],
  surname: [[isRequired(isString), 'Surname is required.']],
}

const rules = {
  forenameSurname: [
    [obj => obj.forename !== obj.surname, 'Forename cannot match surname.'],
  ],
}

const validator = validate(schema, rules)

validator({
  forename: 'foo',
  surname: 'foo',
})
//=> { isValid: false, errors: { property: {}, object: { forenameSurname: ['Forename cannot match surname.'] } } }

Additional properties

By default, if additional properties are present on the object instance which have not been defined on the schema, then an error will be added to errors.property for each additional property, with a default message:

validate({})({ foo: 'bar' })
//=> { isValid: false, errors: { property: { foo: ['Unexpected property'] }, object: {} } }

If you wish to ignore additional properties on the object instance, then you can configure the validate function with the additionalProps.ignore option (see below).

Invalid objects

If the object instance is an invalid object, then the validation result will fail with a default property and message on errors.object:

validate(schema)('foo')
//=> { isValid: false, errors: { property: {}, object: { validObject: 'Invalid object.' } }}

This default property and message can be configured with the invalidObject options (see below).

Configuring validate

You can created a customised version of the validate function by using configure:

import configure from 'inspected/configure'

const options = { ... }
const validate = configure(options)

The available options are:

Option	Default	Description
additionalProps.ignore	false	Flag whether to ignore properties on the object instance which are not defined on the schema.
additionalProps.message	'Unexpected property.'	The message to add to the `errors.property` object when an additional property is found on the object instance. Only applicable when `additionalProps.ignore` is `false`.
invalidObject.property	'validObject'	The property to add to `errors.object` if the object instance is an invalid object.
invalidObject.message	'Invalid object.'	The property message to add to `errors.object` if the object instance is an invalid object.
logger	message => {}	Output validation processing to a logger. The `message` is an object containing `type`, `stage`, `message`, and `data` properties.

Error formatters

You can format the errors object within the validation result by using the supplied error formatters, which is useful for displaying the error messages:

import errorPerProperty from 'inspected/formatters/error-per-property'
import errorPerMessage from 'inspected/formatters/error-per-message'

const schema = {
  name: [
    [isString, 'Name must be a string.'],
    [val => val && val.length > 3, 'Name must be longer than 3 characters.'],
  ],
}

const result = validate(schema)({ name: false })

errorPerProperty(result.errors)
//=> { property: [ { name: 'name', messages: ['Name must be a string.', 'Name must be longer than 3 characters.'] } ], object: [] }

errorPerMessage(result.errors)
//=> { property: [ { name: 'name', message: 'Name must be a string.' }, { name: 'name', message: 'Name must be longer than 3 characters.' } ], object: [] }

Schema functions

Function	Format
isArray	val => bool
isBoolean	val => bool
isEmpty	val => bool
isFunction	val => bool
isNil	val => bool
isObject	val => bool
isOptional	val => predicate => bool
isRequired	val => predicate => bool
isString	val => bool

Recipies

Object of shape

import isRequired from 'inspected/schema/is-required'
import isString from 'inspected/schema/is-string'
import validate from 'inspected/validate'

const userSchema = {
  name: [[isRequired(isString), 'Name is required.']],
}

validate(userSchema)({ name: 'user' }) 
// => { isValid: true, ... }

Optional collection

import isOptional from "inspected/schema/is-optional"
import isArray from "inspected/schema/is-array"
import validate from "inspected/validate"

const departmentSchema = {
  users: [[isOptional(isArray), "Users must be an array."]]
};

validate(departmentSchema)({ users: null }))
// => { isValid: true, ... }

validate(departmentSchema)({ users: [] }))
// => { isValid: true, ... }

validate(departmentSchema)({ users: {} }))
// => { isValid: false, ... }

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