[@zokugun/is-it-type](https://github.com/zokugun/node-is-it-type) ========================================================== [![MIT licensed](https://img.shields.io/badge/license-MIT-blue.svg)](./LICENSE) [![NPM Version](https://img.shields.io/npm/v/@zokugun/is-it-type.svg?colorB=green)](https://www.npmjs.com/package/@zokugun/is-it-type) [![Donation](https://img.shields.io/badge/donate-ko--fi-green)](https://ko-fi.com/daiyam) [![Donation](https://img.shields.io/badge/donate-liberapay-green)](https://liberapay.com/daiyam/donate) [![Donation](https://img.shields.io/badge/donate-paypal-green)](https://paypal.me/daiyam99) Why `@zokugun/is-it-type`? -------------------------- - Zero dependencies. - Predictable naming across primitives, boxed types, iterables, errors, promises, and constructors. - First-class TypeScript support: every helper is a ready-to-use predicate. - `typeOf`/`isType` go beyond native `typeof`, normalizing async vs. sync functions, arrays vs. records, Node.js errors, and more. Getting Started --------------- With [node](http://nodejs.org) previously installed: ``` npm install @zokugun/is-it-type ``` Import only the predicates you need (tree-shaking friendly) and use them as runtime guards: ```typescript import { isNonEmptyArray, isString } from '@zokugun/is-it-type'; function normalizeTags(input: unknown): string[] { if(!isNonEmptyArray(input)) { return []; } return input.filter(isString); } ``` Usage Examples -------------- ### Narrowing unknown data ```typescript import { isRecord, isBooleanLike, isNonNull, toBoolean } from '@zokugun/is-it-type'; function readFeatureFlag(payload: unknown): boolean { if(isRecord(payload) && isBooleanLike(payload.enabled)) { return toBoolean(payload.enabled); } return false; } ``` ### Classifying values with `typeOf` and `isType` ```typescript import {typeOf, isType} from '@zokugun/is-it-type'; const kind = typeOf(value); switch(kind) { case 'array': // Guaranteed array here break; case 'async-function': await value(); break; default: // Handle primitives, records, promises, etc. } if(isType(value, 'date')) { console.log('Timestamp:', value.getTime()); } ``` `typeOf` returns normalized descriptors beyond the native `typeof`, including: `array`, `record`, `date`, `error`, `node-error`, `promise`, `regexp`, `async-function`, `sync-function`, `constructor`, and `generator`, plus the standard primitives (`undefined`, `null`, `boolean`, `number`, `bigint`, `string`, `symbol`). Combine it with `isType` for expressive guards without duplicating comparison logic. Quick Reference --------------- | Predicate | What it checks | | ------------------------- | --------------------------------------------------------------------------------------------------- | | `isActualFunction` | Raw `typeof value === 'function'` check (constructors/classes pass). | | `isActualObject` | Non-null values whose `typeof` is `'object'` (arrays included). | | `isArray` | `Array.isArray` plus an optional per-element predicate. | | `isAsyncGenerator` | Functions whose constructor name is `AsyncGeneratorFunction`. | | `isAsyncIterable` | Objects implementing `Symbol.asyncIterator`. | | `isAsyncFunction` | Functions whose constructor name is `AsyncFunction`. | | `isBigInt` | Primitive `bigint` values. | | `isBigIntLike` | Primitive bigint or boxed `BigInt` objects. | | `isBlankString` | Strings that become empty after `trim()`. | | `isBoolean` | Primitive booleans. | | `isBooleanLike` | Primitive booleans or boxed `Boolean` objects. | | `isBoxedBigInt` | Boxed `BigInt` objects. | | `isBoxedBoolean` | Boxed `Boolean` objects. | | `isBoxedNumber` | Boxed `Number` objects. | | `isBoxedPrimitive` | Boxed `BigInt`, `Boolean`, `Number`, or `String` objects. | | `isBoxedString` | Boxed `String` objects. | | `isConstructor` | Functions whose prototype indicates they should be called with `new`. | | `isDate` | `instanceof Date`. | | `isEmptyArray` | Arrays whose `length` is `0`. | | `isEmptyRecord` | Plain objects with no own enumerable keys. | | `isEmptyString` | Strings of length `0`. | | `isError` | `instanceof Error`. | | `isFinite` | Number-like inputs that are neither `NaN` nor ±`Infinity`. | | `isFunction` | Callables that are not constructors/classes. | | `isGenerator` | Functions whose constructor name is `GeneratorFunction` or `AsyncGeneratorFunction`. | | `isInteger` | Values where `Number.isInteger(value)` succeeds. | | `isIntegerGreaterOrEqual` | Integers greater than or equal to the provided threshold. | | `isIntegerGreaterThan` | Integers strictly greater than the provided threshold. | | `isIntegerLessOrEqual` | Integers less than or equal to the provided threshold. | | `isIntegerLessThan` | Integers strictly less than the provided threshold. | | `isNaN` | Number-like inputs whose numeric value is `NaN`. | | `isIterable` | Objects implementing `Symbol.iterator` or `Symbol.asyncIterator`. | | `isNegativeInteger` | Integers strictly below zero. | | `isNegativeIntegerOrZero` | Integers that are zero or below. | | `isNodeError` | Objects matching `NodeJS.ErrnoException` shape (they expose `code`). | | `isNonBlankString` | Strings containing non-whitespace characters. | | `isNonEmptyArray` | Arrays with at least one element. | | `isNonEmptyRecord` | Plain objects that own at least one key. | | `isNonEmptyString` | Strings whose length is greater than `0`. | | `isNonNull` | Values that are not strictly `null`. | | `isNonNullable` | Values excluding both `null` and `undefined`. | | `isNonUndefined` | Values that are not `undefined`. | | `isNull` | Strict `null` checks. | | `isNullable` | Values that are either `null` or `undefined`. | | `isNumber` | Primitive numbers (including `NaN`/`Infinity`). | | `isNumberLike` | Number or bigint primitives plus boxed `Number`/`BigInt` objects. | | `isObject` | Non-null objects that are not arrays. | | `isObjectLike` | Non-null objects or functions. | | `isPositiveInteger` | Integers strictly above zero. | | `isPositiveIntegerOrZero` | Integers that are zero or above. | | `isPrimitive` | String, number, boolean, or bigint primitives. | | `isPromiseLike` | Objects exposing a callable `then` method. | | `isPromise` | Objects whose constructor is `Promise`. | | `isRecord` | Plain objects (default `Object` constructor, not arrays/arguments). | | `isRegExp` | `instanceof RegExp`. | | `isString` | Primitive strings. | | `isStringLike` | Primitive strings or boxed `String` objects. | | `isSyncGenerator` | Functions whose constructor name is `GeneratorFunction`. | | `isSyncIterable` | Objects implementing `Symbol.iterator`. | | `isSymbol` | Primitive symbols. | | `isSyncFunction` | Functions that are neither constructors, async, nor generator functions. | | `isType` | Wrapper that compares `typeOf(value)` to a `TypesLiteral`. | | `isUndefined` | Strict `undefined` checks. | | `typeOf` | Normalized `typeof` replacement (array, record, async-function, constructor, etc.). | | `toBigInt` | Returns the primitive bigint value from either a primitive or `BigInt` wrapper. | | `toBoolean` | Returns the primitive boolean value from either a primitive or `Boolean` wrapper. | | `toNumber` | Returns the primitive number value from either a primitive or `Number` wrapper. | | `toPrimitive` | Unboxes any boxed primitive (`Boolean`, `Number`, `String`, `BigInt`) to its primitive counterpart. | | `toString` | Returns the primitive string value from either a primitive or `String` wrapper. | Need a normalized descriptor instead of a boolean? Reach for `typeOf` helper function and the `Types`/`TypesLiteral` TypeScript helpers. Donations --------- Support this project by becoming a financial contributor.
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License ------- Copyright © 2025-present Baptiste Augrain Licensed under the [MIT license](https://opensource.org/licenses/MIT).