Type Helpers

Utility functions for working with type operations.

Functions

Function	Description
DeepPartial	Recursively makes all properties of T optional, including nested objects and array elements.
DeepWritable	Recursively removes readonly from all properties of T, including nested objects, array elements, and tuple positions.
isArray	Checks if a value is an array.
isArrayBuffer	Checks if a value is an ArrayBuffer instance.
isArrayLike	Checks if a value is array-like: has a non-negative integer length property.
isAsyncFunction	Checks if a value is an async function.
isAsyncGenerator	Checks if a value is an async generator object (the result of calling an async function*).
isAsyncGeneratorFunction	Checks if a value is an async generator function (an async function* declaration or expression).
isAsyncIterable	Checks if a value implements the async iterable protocol.
isBigInt	Checks if a value is a bigint.
isBlob	Checks if a value is a Blob instance.
isBoolean	Checks if a value is a boolean.
isDate	Checks if a value is a Date instance.
isDefined	Checks if a value is defined (not undefined nor null).
isDirectInstanceOf	native JS value.constructor === Foo (ES1)
isEmpty	Checks if a value is empty.
isError	Checks if a value is an Error instance.
isFalsy	Checks if a value is falsy (false, null, undefined, 0, "", NaN).
isFinite / isFiniteNumber	native JS Number.isFinite(value) (ES2015)
isFormData	Checks if a value is a FormData instance.
isFunction	Checks if a value is a function.
isGenerator	Checks if a value is a generator object (the result of calling a function*).
isGeneratorFunction	Checks if a value is a generator function (a function* declaration or expression).
isHtmlElement / isUrlInstance / isUrlSearchParams	native JS value instanceof HTMLElement / URL / URLSearchParams (Web API)
isInfinite	native JS value === Infinity || value === -Infinity / !Number.isFinite(value) && !Number.isNaN(value) (ES2015)
isInteger	native JS Number.isInteger(value) (ES2015)
isIterable	Checks if a value is iterable (has a Symbol.iterator method).
isMap	Checks if a value is a Map instance.
isNaN	native JS Number.isNaN(value) (ES2015)
isNull	Checks if a value is null.
isNullish	Checks if a value is null or undefined (nullish).
isNumber	Checks if a value is a number.
isPlainObject	Checks if a value is a plain object.
isPrimitive	Checks if a value is a JavaScript primitive.
isPromise	Checks if a value is a Promise or a thenable.
isPromiseLike	Checks if a value is a thenable (has a .then() method).
isPropertyKey	Checks if a value is a valid property key: string, number, or symbol.
isRegExp	Checks if a value is a RegExp instance.
isSafeInteger	native JS Number.isSafeInteger(value) (ES2015)
isSet (Set data structure)	native JS value instanceof Set (ES2015)
isSpecialObject	Determines if a value is a special object that should not have its properties compared deeply.
isString	Checks if a value is a string.
isSymbol	Checks if a value is a symbol.
isTemporalDuration	Checks if a value is a Temporal.Duration.
isTemporalInstant	Checks if a value is a Temporal.Instant.
isTemporalPlainDate	Checks if a value is a Temporal.PlainDate.
isTemporalPlainDateTime	Checks if a value is a Temporal.PlainDateTime.
isTemporalPlainTime	Checks if a value is a Temporal.PlainTime.
isTemporalZonedDateTime	Checks if a value is a Temporal.ZonedDateTime.
isTimestamp	Checks if a value is a valid timestamp (milliseconds or Unix seconds).
isTruthy	Checks if a value is truthy (not false, null, undefined, 0, "", or NaN).
isUndefined	Checks if a value is undefined.
isValidRegex	Checks if a string is a valid regex pattern.
isWeakMap / isWeakSet / isWeakRef	native JS value instanceof WeakMap / WeakSet / WeakRef (ES2015 / ES2021)
TypedArrays (isInt8Array, isFloat32Array, ...)	native JS value instanceof Int8Array / Float32Array / ... (ES2015)