# @typeguards/core > Runtime type checking library for TS & JS Latest version **1.1.0** (published 2021-04-04) · Apache-2.0 license · 0 weekly downloads ## Install ```sh npm install @typeguards/core pnpm add @typeguards/core yarn add @typeguards/core bun add @typeguards/core ``` ## Health **Score 20/100 (F)** — status: abandoned. Positive: esm support; no vulnerabilities. Warnings: low downloads; no types. Negative: abandoned; low maintenance score. ## Facts | | | |---|---| | Version | 1.1.0 | | Published | 2021-04-04 | | First published | 2021-03-29 | | Weekly downloads | 0 | | License | Apache-2.0 | | TypeScript types | none | | Module format | ESM + CommonJS | | Node | >=10 | | Dependencies | 0 | | Unpacked size | 164.3 KB | | Known vulnerabilities | 0 | | Install scripts | no | | GitHub stars | 1 | | Author | Lchemist | | Maintainers | lchemist | | Keywords | type-guard, type-checking, type-validation, runtime-type, runtime-typechecking, runtime-type-checking, runtime-type-validation | ## Links - npm: https://www.npmjs.com/package/@typeguards/core - Repository: https://github.com/Lchemist/TypeGuards - Issues: https://github.com/Lchemist/TypeGuards/issues - npm.io page: https://npm.io/package/@typeguards/core ## Alternatives - [@sindresorhus/slugify](https://npm.io/package/@sindresorhus/slugify.md) — 3.7M weekly downloads - [solid-js](https://npm.io/package/solid-js.md) — 2.7M weekly downloads - [expo-glass-effect](https://npm.io/package/expo-glass-effect.md) — 2.5M weekly downloads - [nanoassert](https://npm.io/package/nanoassert.md) — 780.8K weekly downloads - [@ffmpeg/ffmpeg](https://npm.io/package/@ffmpeg/ffmpeg.md) — 529.5K weekly downloads ## Recent versions - 1.1.0 (latest) — 2021-04-04 - 1.0.0 — 2021-03-29 ## README # TypeGuards [![build](https://github.com/Lchemist/TypeGuards/workflows/build/badge.svg)](https://github.com/Lchemist/TypeGuards/actions?query=workflow%3Abuild) [![Coverage Status](https://img.shields.io/codecov/c/github/Lchemist/TypeGuards/main.svg)](https://codecov.io/gh/Lchemist/TypeGuards/branch/main) [![NPM](https://img.shields.io/npm/v/@typeguards/core.svg)](https://www.npmjs.com/package/@typeguards/core) [![semantic-release](https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg)](https://github.com/semantic-release/semantic-release) [![Commitizen friendly](https://img.shields.io/badge/commitizen-friendly-brightgreen.svg)](https://commitizen.github.io/cz-cli/) [![Conventional Changelog](https://img.shields.io/badge/changelog-conventional-brightgreen.svg)](https://conventional-changelog.github.io) Runtime type checking library for TypeScript & JavaScript. ## ✨ Features * Provides runtime type validation. * Can derive static type from any type guard, thus types are never out of sync. * Supports nested type guards. * Supports almost all JS data types, including Promise, Proxy, DataView and typed arrays. * Package has 0 dependency. ## 📦 Installation ```bash # npm npm install @typeguards/core # yarn yarn add @typeguards/core ``` ## 🔨 Usage ### Basics ```ts import T from '@typeguards/core' T.Number.validates(1) // true T.Number.validates('1') // false T.Optional(T.String).validates('1') // true T.Optional(T.String).validates(undefined) // true T.Optional(T.String).validates(1) // false // Custom type guard const Range = T.Number.config({ // Custom validation function validate: value => typeof value === 'number' && value > 0 && value < 3, }) Range.validate(0) // false Range.validate(1) // true Range.validate(2) // true Range.validate(3) // false ``` ### Schema ```ts import type { Static } from '@typeguards/core' import T, { createSchema } from '@typeguards/core' const Age = T.Number.config({ validate: v => typeof v === 'number' && v >= 0 }) // Custom schema const JobSchema = T.Schema({ title: T.String, salary: T.Nullable(T.Number), }) // Use closure to use type guard directly & prevent naming conflicts with JS built-in objects const PersonSchema = createSchema(({ Boolean, String, Number, Array, Optional, Union }) => ({ name: String, age: Age, alive: Boolean, address: Optional(String), // Support complex nested type guard favorites: Array(Union(String, Number)), // Support nested schema job: JobSchema, })) // Support static type derivation, thus type is never out of sync const person: Static = { name: 'John Doe', age: 23, alive: true, address: undefined, favorites: ['cat', 'dog', 7], job: { title: 'Dreamer', salary: null, }, } PersonSchema.validate(person) // true PersonSchema.validate({ ...person, address: undefined }) // true, because address is optional PersonSchema.validate({ ...person, name: undefined }) // false PersonSchema.validate({ ...person, age: '23' }) // false const CatSchema = T.Partial(T.Pick(PersonSchema, ['name', 'age', 'alive'])) // Equivalent to Partial> type Cat = Static CatSchema.validate(person) // false CatSchema.validate({ name: 'Baby', age: undefined }) // true // Retrieve Schema definition const catDefinition = CatSchema.definition() // { name: String, age: Age, alive: Boolean } // Retrieve Indexed access type definition, which is a type guard in this case const CatName = CatSchema.definition('name') // T.String CatName.validate('str') // true catDefinition.name.validate('str') // true ``` ### Transformer (Experimental Feature) ```ts import T from '@typeguards/core' // Customize transformation function const Name = T.String.config({ transform: val => `${val} Jr.` }) const Alive = T.Boolean.config({ transform: val => val ?? true }) const Person = T.Partial(T.Schema({ name: Name, alive: Alive })) const john = { name: 'John' } Person.validate(john) // true const johnJr = Person.transform(john) // { name: 'John Jr.', alive: true } ``` ## 🛡️ List of type guards | name | description |-------------------|-------------------------------------------------------------------------------------------------------- | Boolean | | StringBoolean | "true" \| "TRUE" \| "false" \| "FALSE" \| "1" \| "0" | Number | | NaN | `NaN` | PositiveNumber | A number value that's greater than 0 | NegativeNumber | A number value that's less than 0 | BigInt | | PositiveBigInt | A BigInt value that's greater than 0 | NegativeBigInt | A BigInt value that's less than 0 | StringNumber | A string whose value is a number, such as "0", "-1", "3.333" | String | | NonEmptyString | A string that's not empty even after trimming | Symbol | | Undefined | `undefined` | Null | `null` | Object | An object (Any object will qualify as long as `typeof obj === 'object'`) | RegExp | | Map | | WeakMap | | Set | | WeakSet | | Promise | | Proxy | | Date | | StringDate | A correctly formatted date string, such as "1996-07-23", "1996/07/23", "1996 Jul", "1996" | Array | | StringArray | A string whose value is an array separated by delimiter "," (delimiter is customizable) | ArrayBuffer | | SharedArrayBuffer | | DataView | | Int8Array | | Uint8Array | | Uint8ClampedArray | | Int16Array | | Uint16Array | | Int32Array | | Uint32Array | | Float32Array | | Float64Array | | BigInt64Array | | BigUint64Array | | Function | A function | Schema | A plain object | Optional | T \| undefined | Nullable | T \| null | Never | Equivalent of TypeScript `never` type | Unknown | Equivalent of TypeScript `unknown` type | Any | Equivalent of TypeScript `any` type | Record | Equivalent of TypeScript `Record` type | Partial | Equivalent of TypeScript `Partial` type | Required | Equivalent of TypeScript `Required` type | Pick | Equivalent of TypeScript `Pick` type | Omit | Equivalent of TypeScript `Omit` type | NonNullable | Equivalent of TypeScript `NonNullable` type | Union | Equivalent of TypeScript union type | Const | Equivalent of TypeScript const assertion | GeneratorFunction | Requires ES6/ES2015 or later | Generator | Requires ES6/ES2015 or later | AsyncFunction | Requires ES8/ES2017 or later ## 📜 License [Apache License 2.0](/LICENSE) --- _Source: https://npm.io/package/@typeguards/core · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._