@lutlelk-tools/core

Core utility library providing type guards and common helper functions for JavaScript/TypeScript.

Installation

npm install @lutlelk-tools/core
# or
pnpm add @lutlelk-tools/core
# or
yarn add @lutlelk-tools/core

Usage

import { isString, isNumber, isEmpty, noop, times } from '@lutlelk-tools/core'

API

Type Guards

isString(value: unknown): value is string

Check if value is a string.

isString('hello') // => true
isString(123) // => false

isNumber(value: unknown): value is number

Check if value is a number (not NaN).

isNumber(123) // => true
isNumber(NaN) // => false
isNumber('123') // => false

isBoolean(value: unknown): value is boolean

Check if value is a boolean.

isBoolean(true) // => true
isBoolean(1) // => false

isNull(value: unknown): value is null

Check if value is null.

isNull(null) // => true
isNull(undefined) // => false

isUndefined(value: unknown): value is undefined

Check if value is undefined.

isUndefined(undefined) // => true
isUndefined(null) // => false

isNil(value: unknown): value is null | undefined

Check if value is null or undefined.

isNil(null) // => true
isNil(undefined) // => true
isNil(0) // => false

isFunction(value: unknown): value is (...args: any[]) => any

Check if value is a function.

isFunction(() => {}) // => true
isFunction('function') // => false

isArray(value: unknown): value is any[]

Check if value is an array.

isArray([1, 2, 3]) // => true
isArray({}) // => false

isObject(value: unknown): value is Record<string, any>

Check if value is an object (not null, not array).

isObject({}) // => true
isObject([]) // => false
isObject(null) // => false

isPlainObject(value: unknown): value is Record<string, any>

Check if value is a plain object (created by Object or null prototype).

isPlainObject({}) // => true
isPlainObject(new Date()) // => false
isPlainObject([]) // => false

isEmpty(value: unknown): boolean

Check if value is empty.

isEmpty('') // => true
isEmpty([]) // => true
isEmpty({}) // => true
isEmpty(null) // => true
isEmpty([1]) // => false

Utility Functions

noop(): void

A no-operation function.

noop() // Does nothing

identity<T>(value: T): T

Returns the first argument.

identity(42) // => 42
identity('hello') // => 'hello'

times<T>(n: number, iteratee: (index: number) => T): T[]

Call iteratee n times and return results.

times(3, i => i * 2)
// => [0, 2, 4]

toString(value: unknown): string

Convert value to string.

toString(123) // => '123'
toString({ a: 1 }) // => '{"a":1}'
toString(null) // => ''

toNumber(value: unknown): number

Convert value to number.

toNumber('123') // => 123
toNumber('abc') // => 0
toNumber(true) // => 1

toBoolean(value: unknown): boolean

Convert value to boolean.

toBoolean('true') // => true
toBoolean('false') // => false
toBoolean(1) // => true
toBoolean(0) // => false

isStrictEqual(a: unknown, b: unknown): boolean

Strict equality check.

isStrictEqual(1, 1) // => true
isStrictEqual(1, '1') // => false

License

ISC