- 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/isTypego beyond nativetypeof, normalizing async vs. sync functions, arrays vs. records, Node.js errors, and more.
With node previously installed:
npm install @zokugun/is-it-type Import only the predicates you need (tree-shaking friendly) and use them as runtime guards:
import { isNonEmptyArray, isString } from '@zokugun/is-it-type'; function normalizeTags(input: unknown): string[] { if(!isNonEmptyArray(input)) { return []; } return input.filter(isString); }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; }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.
| 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.
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Copyright © 2025-present Baptiste Augrain
Licensed under the MIT license.