Is

The definitive collection of is* functions for runtime type checking. Realms support, tree-shakable, with types.

Every function provided accepts a single argument of unknown type and returns a boolean, almost always as a TypeScript type guard.

Install

npm install is@npm:@fabiospampinato/is

Functions

| Primitives | Boxed Primitives | Built-ins | DOM | Typed Array | | --------------------------- | ------------------------------------- | ------------------------------------------- | ----------------------------------------- | ------------------------------------------- | | isPrimitive | isBoxedPrimitive | isArray | isAttribute | isTypedArray | | isBigInt | isBoxedBigInt | isArguments | isComment | isInt8Array | | isBoolean | isBoxedBoolean | isArrayBuffer | isDocument | isInt16Array | | isNil | isBoxedNumber | isArrayLike | isDocumentFragment | isInt32Array | | isNull | isBoxedString | isAsyncIterable | isDocumentType | isUint8Array | | isNumber | isBoxedSymbol | isBlob | isElement | isUint8ClampedArray | | isString | | isBuffer | isNode | isUint16Array | | isSymbol | | isClass | isText | isUint32Array | | isUndefined | | isDataView | isWindow | isFloat32Array | | | | isDate | | isFloat64Array | | | | isError | | isBigInt64Array | | | | isIterable | | isBigUint64Array | | | | isMap | | | | | | isNative | | | | | | isPromise | | | | | | isRegExp | | | | | | isSet | | | | | | isSharedArrayBuffer | | | | | | isWeakMap | | | | | | isWeakRef | | | | | | isWeakSet | | |

| Function | Number | Object | Others | | ----------------------------------------------------- | --------------------------------- | --------------------------------------- | ----------------------------------- | | isArrowFunction | isEven | isArrayLikeObject | isDefined | | isAsyncFunction | isFinite | isFrozen | isEmpty | | isAsyncGeneratorFunction | isFloat | isObject | isFalsy | | isBoundFunction | isInteger | isObjectLike | isTruthy | | isFunction | isLength | isPlainObject | isWeakReferable | | isGeneratorFunction | isNaN | isPrototype | | | | isNegativeZero | isSealed | | | | isNumberLike | | | | | isOdd | | | | | isSafeInteger | | |

Usage

isArguments

Checks if a value is an arguments object.

import {isArguments} from 'is';

const args = (function () { return arguments; })();

isArguments ( args ); // => true
isArguments ( [] ); // => false

isArrayBuffer

Checks if a value is an ArrayBuffer object.

import {isArrayBuffer} from 'is';

isArrayBuffer ( new ArrayBuffer ( 8 ) ); // => true
isArrayBuffer ( [] ); // => false

isArrayLikeObject

Checks if a value is an Array-like object, meaning a non-string and non-function with an integer length property.

import {isArrayLikeObject} from 'is';

isArrayLikeObject ( [] ); // => true
isArrayLikeObject ( { length: 1 } ); // => true
isArrayLikeObject ( 'foo' ); // => false
isArrayLikeObject ( isArrayLikeObject ); // => false

isArrayLike

Checks if a value is an Array-like object, meaning a non-function with an integer length property.

import {isArrayLike} from 'is';

isArrayLike ( [] ); // => true
isArrayLike ( { length: 1 } ); // => true
isArrayLike ( 'foo' ); // => true
isArrayLike ( isArrayLike ); // => false

isArray

Checks if a value is an Array.

import {isArray} from 'is';

isArray ( [] ); // => true
isArray ( {} ); // => false

isArrowFunction

Checks if a value is an arrow function. There's a detectable difference between regular and arrow functions.

import {isArrowFunction} from 'is';

isArrowFunction ( () => {} ); // => true
isArrowFunction ( function () {} ); // => false

isAsyncFunction

Checks if a value is an async function. Note that this will return false for async generator functions.

import {isAsyncFunction} from 'is';

isAsyncFunction ( async () => {} ); // => true
isAsyncFunction ( () => {} ); // => false

isAsyncGeneratorFunction

Checks if a value is an async generator function.

import {isAsyncGeneratorFunction} from 'is';

isAsyncGeneratorFunction ( function* () {} ); // => true
isAsyncGeneratorFunction ( function () {} ); // => false

isAsyncIterable

Checks if a value is an async iterable.

import {isAsyncIterable} from 'is';

const myAsyncIterable = {
  async * [Symbol.asyncIterator]() {
    yield 'hello';
  }
};

isAsyncIterable ( myAsyncIterable ); // => true
isAsyncIterable ( [] ); // => false

isAttribute

Checks if a value is likely a DOM attribute.

import {isAttribute} from 'is';

isAttribute ( document.createAttribute ( 'foo' ) ); // => true
isAttribute ( body ); // => false

isBigInt

Checks if a value is a bigint.

import {isBigInt} from 'is';

isBigInt ( 0n ); // => true
isBigInt ( 0 ); // => false

isBigInt64Array

Checks if a value is a BigInt64Array.

import {isBigInt64Array} from 'i