maybe.md

maybe

Creates a type-validation that checks if a value is of validated type, undefined, and optionally null.

Type parameters

T

The concrete type that is validated if a value is not undefined nor null.

Parameters

validator

A type-validation to check values that are not null nor undefined.

Type: AnyTypeValidation<T>

withNull

If true the returned type-validation accepts null as well.
Otherwise, the returned type-validation only accepts undefined, or whatever validator accepts.

Type: boolean | undefined

Return type

A type-validation;
If withNull is true then TypeValidation<T | undefined | null>;
Otherwise, TypeValidation<T | undefined>.

Example

import { maybe, objectOf, typeValidatorType } from '@altostra/type-validations'

const maybeObject = maybe(objectOf({}))
const maybeNullableObject = maybe(objectOf({}), true)

console.log(maybeObject[typeValidatorType]) /* ?({
  [*]: *
}) */
console.log(maybeNullableObject[typeValidatorType]) /* ?({
  [*]: *
} | null) */

console.log(maybeObject(console.log, console.log)) // true
console.log(maybeObject({}, console.log)) // true
console.log(maybeObject([], console.log)) // true
console.log(maybeObject(undefined, console.log)) // true

console.log(maybeNullableObject(console.log, console.log)) // true
console.log(maybeNullableObject({}, console.log)) // true
console.log(maybeNullableObject([], console.log)) // true
console.log(maybeNullableObject(undefined, console.log)) // true
console.log(maybeNullableObject(null, console.log)) // true

console.log(maybeObject(null, console.log)) /* {
  path: [],
  reason: 'Value <null> is not <undefined> nor {\n  [*]: *\n}',
  propertyType: '?({\n  [*]: *\n})'
}
{
  path: [],
  reason: 'Value <null> is not an object',
  propertyType: '{\n  [*]: *\n}'
}
false */
console.log(maybeObject('string', console.log)) /* {
  path: [],
  reason: "Value <'string'> is not <undefined> nor {\n  [*]: *\n}",
  propertyType: '?({\n  [*]: *\n})'
}
{
  path: [],
  reason: "Value <'string'> is not an object",
  propertyType: '{\n  [*]: *\n}'
}
false */
console.log(maybeNullableObject('object', console.log)) /* {
  path: [],
  reason: "Value <'object'> is not <undefined>, <null>, nor {\n  [*]: *\n} | null",
  propertyType: '?({\n  [*]: *\n} | null)'
}
{
  path: [],
  reason: "Value <'object'> is not an object",
  propertyType: '{\n  [*]: *\n}'
}
false */

const maybeObjectIncognito: unknown = {}
const maybeNullableObjectIncognito: unknown = null

if (maybeObject(maybeObjectIncognito) && maybeObjectIncognito) {
    console.log(Object.keys(maybeObjectIncognito)) // []
}

if (maybeNullableObject(maybeNullableObjectIncognito)) {
    console.log(maybeNullableObjectIncognito) // null
}