# @alloc/is

> Runtime type checking

Latest version **3.1.6** (published 2024-05-29) · MIT license · 0 weekly downloads

## Install

```sh
npm install @alloc/is
pnpm add @alloc/is
yarn add @alloc/is
bun add @alloc/is
```

## Health

**Score 30/100 (F)** — status: abandoned.

Positive: has types; esm support; no vulnerabilities; high quality score.

Warnings: low downloads.

Negative: abandoned; low maintenance score.

## Facts

| | |
|---|---|
| Version | 3.1.6 |
| Published | 2024-05-29 |
| First published | 2019-11-20 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | bundled |
| Module format | ESM + CommonJS |
| Dependencies | 0 |
| Unpacked size | 42.8 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 4 |
| Maintainers | aleclarson |

## Links

- npm: https://www.npmjs.com/package/@alloc/is
- Repository: https://github.com/alloc/is
- Homepage: https://github.com/alloc/is#readme
- Issues: https://github.com/alloc/is/issues
- npm.io page: https://npm.io/package/@alloc/is

## Recent versions

- 3.1.6 (latest) — 2024-05-29
- 3.1.5 — 2024-05-05
- 3.1.4 — 2024-05-05
- 3.1.3 — 2023-05-18
- 3.1.2 — 2022-01-24
- 3.1.1 — 2021-06-15
- 3.1.0 — 2021-03-27
- 3.0.0 — 2021-02-24
- 2.1.2 — 2020-08-07
- 2.1.1 — 2019-12-17
- 2.1.0 — 2019-12-16
- 2.0.0 — 2019-12-15
- 1.2.0 — 2019-11-20

## README

# @alloc/is

Runtime type checking for TypeScript (inspired by `@sindresorhus/is`)

- **isomorphic** (no DOM or NodeJS types)
- **type guards** (for type narrowing)
- **fully tested** (each possible type is tested on every type checker)

## Usage

First, do `yarn add is@npm:@alloc/is` if you never use the `npm` CLI.
Otherwise, you need to import `@alloc/is` instead of `is`.

```ts
import { is } from 'is'

//
// Get the type name of a value.
// Object types are camel case.
//

isWhat(0) // 'number'
isWhat({}) // 'Object'

//
// Check the constructor of a value.
//

isType(0, Number) // true
isType({}, Object) // true
isType([], Object) // false

//
// Find a constructor in a value's prototype chain.
//

isKind([], Object) // true

//
// Check if the value is a specific type.
//

isNumber(0) // true
isArray([]) // true
```

**See the tests for expected behavior.** They are very readable, just search for `test(`
to jump between the tests of each `is.` function.

## API

[1]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Inheritance_and_the_prototype_chain
[2]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/asyncIterator
[3]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function*
[4]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/iterator

- `isWhat(value)` Get the type name of a value
- `isType(value, constructor)` Check the constructor of a value
- `isKind(value, constructor)` Find a constructor in a value's [prototype chain][1]
- `isArray(value)` Same as `Array.isArray`
- `isAsyncFunction(value)`
- `isAsyncIterable(value)` Returns true for objects returned by [`Symbol.asyncIterator`][2] functions
- `isBigint(value)`
- `isBoolean(value)`
- `isClass(value)` Returns true for `class` functions (but not transpiled classes)
- `isDate(value)`
- `isDefined(value)` The opposite of `isUndefined`
- `isEmptyObject(value)` Returns true for plain objects with no keys
- `isError(value)`
- `isGenerator(value)` Returns true for objects returned by [generator functions][3]
- `isGeneratorFunction(value)`
- `isFunction(value)`
- `isInfinite(value)`
- `isInteger(value)`
- `isIterable(value)` Returns true for objects returned by [`Symbol.iterator`][4] functions
- `isMap(value)`
- `isNan(value)` Same as `Number.isNaN`
- `isNull(value)`
- `isNumber(value)` Returns true for any number (but never `NaN`)
- `isObject(value)` Returns true for any object or function (but never `null`)
- `isPlainObject(value)` Returns true for objects created by `{}`, `new Object`, or `Object.create(null)`
- `isPromise(value)`
- `isPromiseLike(value)` Returns true for objects with a `then` method
- `isRegExp(value)`
- `isSafeInteger(value)` Same as `Number.isSafeInteger`
- `isSet(value)`
- `isString(value)`
- `isSymbol(value)`
- `isUndefined(value)`
- `isWeakMap(value)`
- `isWeakSet(value)`

---
_Source: https://npm.io/package/@alloc/is · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._