@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)`