@xylabs/typeof/src/is.ts

Base functionality used throughout XY Labs TypeScript/JavaScript libraries

export type AnyFunction = (...args: unknown[]) => unknown
export type RecordKey = string | number | symbol

export function isUndefined(value: unknown): value is undefined
export function isUndefined<T>(value: T): value is Extract<T, undefined>
export function isUndefined(value: unknown): value is undefined {
  return value === undefined
}

export function isDefined<T>(value: T): value is Exclude<T, undefined> {
  return !isUndefined(value)
}

export function isNull(value: unknown): value is null
export function isNull<T>(value: T): value is Extract<T, null>
export function isNull(value: unknown): value is null {
  return value === null
}

export function isDefinedNotNull<T>(value: T): value is Exclude<T, undefined | null> {
  return !isUndefined(value) && !isNull(value)
}

export function isUndefinedOrNull(value: unknown): value is undefined | null
export function isUndefinedOrNull<T>(value: T): value is Extract<T, undefined | null>
export function isUndefinedOrNull(value: unknown): value is undefined | null {
  return isUndefined(value) || isNull(value)
}

export function isBigInt(value: unknown): value is bigint
export function isBigInt<T extends bigint>(value: T): value is Extract<T, bigint>
export function isBigInt(value: unknown): value is bigint {
  return typeof value === 'bigint'
}

export function isString(value: unknown): value is string
export function isString<T extends string>(value: T): value is Extract<T, string>
export function isString(value: unknown): value is string {
  return typeof value === 'string'
}

export function isNumber(value: unknown): value is number
export function isNumber<T extends number>(value: T): value is Extract<T, number>
export function isNumber(value: unknown): value is number {
  return typeof value === 'number'
}

export function isObject(value: unknown): value is object
export function isObject<T extends object>(value: T): value is Extract<T, object>
export function isObject(value: unknown): value is object {
  return (typeof value === 'object') && (value !== null) && !Array.isArray(value)
}

export function isArray(value: unknown): value is readonly unknown[]
export function isArray<T>(value: T): value is Extract<T, readonly unknown[]>
export function isArray(value: unknown): value is readonly unknown[] {
  return Array.isArray(value)
}

export function isFunction(value: unknown): value is AnyFunction
export function isFunction<T extends AnyFunction>(value: T): value is Extract<T, AnyFunction>
export function isFunction(value: unknown): value is AnyFunction {
  return typeof value === 'function'
}

export function isSymbol(value: unknown): value is symbol
export function isSymbol<T extends symbol>(value: T): value is Extract<T, symbol>
export function isSymbol(value: unknown): value is symbol {
  return typeof value === 'symbol'
}

export function isEmptyObject(value: unknown): value is {}
export function isEmptyObject<K extends RecordKey, V, T extends Record<K, V>>(value: T): value is Extract<T, Record<K, never>>
export function isEmptyObject(value: unknown): value is {} {
  return isObject(value) && Object.keys(value).length === 0
}

export function isEmptyString(value: unknown): value is ''
export function isEmptyString<T extends string>(value: T): value is Extract<T, ''>
export function isEmptyString(value: unknown): value is '' {
  return isString(value) && value.length === 0
}

export function isEmptyArray(value: unknown): value is []
export function isEmptyArray<T extends Array<unknown>>(value: T): value is Extract<T, Array<unknown>>
export function isEmptyArray(value: unknown): value is [] {
  return isArray(value) && value.length === 0
}

export function isPopulatedArray(value: unknown): value is readonly unknown[]
export function isPopulatedArray<T extends Array<unknown>>(value: T): value is Extract<T, readonly unknown[]>
export function isPopulatedArray(value: unknown): value is readonly unknown[] {
  return isArray(value) && value.length > 0
}

export function isEmpty<T>(value: unknown): value is T
export function isEmpty<K extends RecordKey, V, T extends Record<K, V>>(value: T): value is Extract<T, Record<K, never>>
export function isEmpty<T extends Array<unknown>>(value: T): value is Extract<T, Array<never>>
export function isEmpty<T>(value: unknown): value is T {
  return isEmptyString(value) || isEmptyArray(value) || isEmptyObject(value)
}

export function isFalsy<T>(value: T): value is Extract<T, 0 | null | undefined | false | '' | 0n>
export function isFalsy<T extends boolean>(value: T): value is Extract<T, false>
export function isFalsy<T extends number>(value: T): value is Extract<T, 0>
export function isFalsy<T extends bigint>(value: T): value is Extract<T, 0n>
export function isFalsy<T extends null>(value: T): value is Extract<T, null>
export function isFalsy<T extends undefined>(value: T): value is Extract<T, undefined>
export function isFalsy<T extends string>(value: T): value is Extract<T, ''>
export function isFalsy<T>(value: T): value is T {
  return !value
}

export function isTruthy<T>(value: T): value is Exclude<T, 0 | null | undefined | false | '' | 0n>
export function isTruthy<T extends boolean>(value: T): value is Extract<T, true>
export function isTruthy<T extends number>(value: T): value is Extract<T, number>
export function isTruthy<T extends bigint>(value: T): value is Extract<T, bigint>
export function isTruthy<T extends null>(value: T): value is Extract<T, null>
export function isTruthy<T extends undefined>(value: T): value is Extract<T, undefined>
export function isTruthy<T extends string>(value: T): value is Extract<T, string>
export function isTruthy<T>(value: T): value is T {
  return !!value
}

export function isBoolean(value: unknown): value is boolean
export function isBoolean<T extends boolean>(value: T): value is Extract<T, boolean>
export function isBoolean(value: unknown): value is boolean {
  return typeof value === 'boolean'
}

export function isDateString(value: unknown): value is string
export function isDateString<T>(value: T): value is Extract<T, string>
export function isDateString(value: unknown): value is string {
  return isString(value) && !Number.isNaN(Date.parse(value))
}

export function isDate(value: unknown): value is Date
export function isDate<T>(value: T): value is Extract<T, Date>
export function isDate(value: unknown): value is Date {
  return value instanceof Date
}

export function isRegExp(value: unknown): value is RegExp
export function isRegExp<T extends RegExp>(value: T): value is Extract<T, RegExp>
export function isRegExp(value: unknown): value is RegExp {
  return value instanceof RegExp
}

export function isError(value: unknown): value is Error
export function isError<T>(value: T): value is Extract<T, Error>
export function isError(value: unknown): value is Error {
  return value instanceof Error
}

export function isPromise(value: unknown): value is Promise<unknown>
export function isPromise<T>(value: T): value is Extract<T, Promise<unknown>>
export function isPromise(value: unknown): value is Promise<unknown> {
  return value instanceof Promise
}

export function isPromiseLike(value: unknown): value is Promise<unknown>
export function isPromiseLike<T>(value: T): value is Extract<T, Promise<unknown>>
export function isPromiseLike(value: unknown): value is Promise<unknown> {
  return (
    typeof value === 'object'
    && value !== null
    && typeof (value as Record<string, unknown>).then === 'function'
  )
}

export function isMap(value: unknown): value is Map<unknown, unknown>
export function isMap<K, V, T extends Map<K, V>>(value: T): value is Extract<T, Map<K, V>>
export function isMap(value: unknown): value is Map<unknown, unknown> {
  return value instanceof Map
}

export function isArrayBufferView(value: unknown): value is ArrayBufferView
export function isArrayBufferView<T extends ArrayBufferView>(value: T): value is Extract<T, ArrayBufferView>
export function isArrayBufferView(value: unknown): value is ArrayBufferView {
  return ArrayBuffer.isView(value)
}

export function isSet(value: unknown): value is Set<unknown>
export function isSet<T extends Set<unknown>>(value: unknown | Set<T>): value is Extract<T, Set<unknown>>
export function isSet(value: unknown): value is Set<unknown> {
  return value instanceof Set
}

export function isWeakMap(value: unknown): value is WeakMap<WeakKey, unknown>
export function isWeakMap<K extends WeakKey, V, T extends WeakMap<K, V>>(value: T): value is Extract<T, WeakMap<K, V>>
export function isWeakMap(value: unknown): value is WeakMap<WeakKey, unknown> {
  return value instanceof WeakMap
}

export function isWeakSet(value: unknown): value is WeakSet<WeakKey>
export function isWeakSet<K extends WeakKey, T extends WeakSet<K>>(value: T): value is Extract<T, WeakSet<K>>
export function isWeakSet(value: unknown): value is WeakSet<WeakKey> {
  return value instanceof WeakSet
}

export function isDataView(value: unknown): value is DataView
export function isDataView<T>(value: T): value is Extract<T, DataView>
export function isDataView(value: unknown): value is DataView {
  return value instanceof DataView
}

export function isBlob(value: unknown): value is Blob
export function isBlob<T extends Blob>(value: T): value is Extract<T, Blob>
export function isBlob(value: unknown): value is Blob {
  return typeof Blob !== 'undefined' && value instanceof Blob
}

export function isFile(value: unknown): value is File
export function isFile<T extends File>(value: T): value is Extract<T, File>
export function isFile(value: unknown): value is File {
  return typeof File !== 'undefined' && value instanceof File
}