type-check-lib

Fast, small data validator Inspired by spectypes

Getting started

Install the package:

npm i type-check-lib

Reference

Primitive validators

• boolean
• literal
• nullish
• number
• string
• unknown

Complex validators

• array
• filter
• limit
• map
• object
• optional
• record
• template
• tuple
• union

Examples

Primitive validators

boolean

import { boolean } from 'type-check-lib'

const check = boolean

expect(check(true)).toEqual({
  tag: 'success',
  success: true
})

expect(check('false')).toEqual({
  tag: 'failure',
  failure: {
    value: 'false',
    errors: [{ issue: 'not a boolean', path: [] }]
  }
})

literal

import { literal } from 'type-check-lib'

const check = literal('test')

expect(check('test')).toEqual({
  tag: 'success',
  success: 'test'
})

expect(check('temp')).toEqual({
  tag: 'failure',
  failure: {
    value: 'temp',
    errors: [{ issue: "not a 'test' string literal", path: [] }]
  }
})

nullish

import { nullish } from 'type-check-lib'

const check = nullish

expect(check(undefined)).toEqual({
  tag: 'success'
  success: undefined
})

expect(check(null)).toEqual({
  tag: 'success'
  success: undefined
})

expect(check(123)).toEqual({
  tag: 'failure',
  failure: {
    value: 'temp',
    errors: [{ issue: "not 'null' or 'undefined'", path: [] }]
  }
})

number

import { number } from 'type-check-lib'

const check = number

expect(check(0)).toEqual({
  tag: 'success',
  success: 0
})

expect(check({})).toEqual({
  tag: 'failure',
  failure: {
    value: {},
    errors: [{ issue: 'not a number', path: [] }]
  }
})

string

import { string } from 'type-check-lib'

const check = string

expect(check('')).toEqual({
  tag: 'success',
  success: ''
})

expect(check(null)).toEqual({
  tag: 'failure',
  failure: {
    value: null,
    errors: [{ issue: 'not a string', path: [] }]
  }
})

unknown

import { unknown } from 'type-check-lib'

const check = unknown

expect(check('anything')).toEqual({
  tag: 'success',
  success: 'anything'
})

Complex validators

array

import { array, number } from 'type-check-lib'

const check = array(number)

expect(check([1, 2, 3])).toEqual({
  tag: 'success',
  success: [1, 2, 3]
})

expect(check({ 0: 1 })).toEqual({
  tag: 'failure',
  failure: {
    value: { 0: 1 },
    errors: [{ issue: 'not an array', path: [] }]
  }
})

expect(check([1, 2, '3', false])).toEqual({
  tag: 'failure',
  failure: {
    value: [1, 2, '3', false],
    errors: [
      { issue: 'not a number', path: [2] },
      { issue: 'not a number', path: [3] }
    ]
  }
})

filter

import { array, number, filter } from 'type-check-lib'

const check = array(filter(filter(number, (x) => x < 10), (x) => x > 1))

expect(check([1, 2, 3, 11])).toEqual({
  tag: 'success',
  success: [2, 3]
})

expect(check([1, 2, null])).toEqual({
  tag: 'failure',
  failure: {
    value: [1, 2, null],
    errors: [{ issue: 'not a number', path: [2] }]
  }
})

limit

import { number, limit } from 'type-check-lib'

const check = limit(number, (x) => x > 1)

expect(check(5)).toEqual({
  tag: 'success',
  success: 5
})

expect(check(-5)).toEqual({
  tag: 'failure',
  failure: {
    value: -5,
    errors: [{ issue: 'does not fit the limit', path: [] }]
  }
})

expect(check('5')).toEqual({
  tag: 'failure',
  failure: {
    value: '5',
    errors: [{ issue: 'not a number', path: [] }]
  }
})

map

import { number, map } from 'type-check-lib'

const check = map(number, (x) => x + 1)

expect(check(10)).toEqual({
  tag: 'success',
  success: 11
})

expect(check(undefined)).toEqual({
  tag: 'failure',
  failure: {
    value: undefined,
    errors: [{ issue: 'not a number', path: [] }]
  }
})

object

import { object, number, string, boolean } from 'type-check-lib'

const check = object({ x: number, y: string, z: boolean })

expect(check({ x: 1, y: '2', z: false })).toEqual({
  tag: 'success',
  success: { x: 1, y: '2', z: false }
})

expect(check({ x: 1, y: '2', z: false, xyz: [] })).toEqual({
  tag: 'failure',
  failure: {
    value: { x: 1, y: '2', z: false, xyz: [] },
    errors: [{ issue: 'excess key - xyz', path: [] }]
  }
})

expect(check({})).toEqual({
  tag: 'failure',
  failure: {
    value: {},
    errors: [
      { issue: 'not a number', path: ['x'] },
      { issue: 'not a string', path: ['y'] },
      { issue: 'not a boolean', path: ['z'] }
    ]
  }
})

expect(check([])).toEqual({
  tag: 'failure',
  failure: {
    value: [],
    errors: [{ issue: 'not an object', path: [] }]
  }
})

optional

import { optional, struct, number } from 'type-check-lib'

const check = struct({ x: optional(number) })

expect(check({ x: 5 })).toEqual({
  tag: 'success',
  success: { x: 5 }
})

expect(check({ x: undefined })).toEqual({
  tag: 'success',
  success: { x: undefined }
})

expect(check({})).toEqual({
  tag: 'success',
  success: {}
})

expect(check({ x: 'x' })).toEqual({
  tag: 'failure',
  failure: {
    value: { x: 'x' },
    errors: [{ issue: 'not a number', path: ['x'] }]
  }
})

record

import { record, boolean } from 'type-check-lib'

const check = record(boolean)

expect(check({ foo: false, bar: true })).toEqual({
  tag: 'success',
  success: { foo: false, bar: true }
})

expect(check(true)).toEqual({
  tag: 'failure',
  failure: {
    value: true,
    errors: [{ issue: 'not an object', path: [] }]
  }
})

expect(check({ toString: true })).toEqual({
  tag: 'failure',
  failure: {
    value: { toString: true },
    errors: [{ issue: "includes banned 'toString' key", path: [] }]
  }
})

template

import { template, literal, number, string, boolean } from 'type-check-lib'

const check = template(literal('test'), string, number, boolean)

expect(check('test___123false')).toEqual({
  tag: 'success',
  success: 'test___123false'
})

expect(check('test___false')).toEqual({
  tag: 'failure',
  failure: {
    value: 'test___false',
    errors: [{ issue: 'template literal mismatch', path: [] }]
  }
})

tuple

import { tuple, number, string, boolean } from 'type-check-lib'

const check = tuple(number, string, boolean)

expect(check([1, '2', false])).toEqual({
  tag: 'success',
  success: [1, '2', false]
})

expect(check([])).toEqual({
  tag: 'failure',
  failure: {
    value: [],
    errors: [{ issue: 'length is not 3', path: [] }]
  }
})

expect(check([1, '2', false, 1000])).toEqual({
  tag: 'failure',
  failure: {
    value: [1, '2', false, 1000],
    errors: [{ issue: 'length is not 3', path: [] }]
  }
})

expect(check(['1', '2', 'false'])).toEqual({
  tag: 'failure',
  failure: {
    value: ['1', '2', 'false'],
    errors: [
      { issue: 'not a number', path: [0] },
      { issue: 'not a boolean', path: [2] }
    ]
  }
})

union

import { union, number, string, boolean } from 'type-check-lib'

const check = union(number, string, boolean)

expect(check('temp')).toEqual({
  tag: 'success',
  success: 'temp'
})

expect(check(true)).toEqual({
  tag: 'success',
  success: true
})

expect(check(null)).toEqual({
  tag: 'failure',
  failure: {
    value: null,
    errors: [
      { issue: 'union case #0 mismatch: not a number', path: [] },
      { issue: 'union case #1 mismatch: not a string', path: [] },
      { issue: 'union case #2 mismatch: not a boolean', path: [] }
    ]
  }
})