npm package discovery and stats viewer.

Discover Tips

  • General search

    [free text search, go nuts!]

  • Package details

    pkg:[package-name]

  • User packages

    @[username]

Sponsor

Optimize Toolset

I’ve always been into building performant and accessible sites, but lately I’ve been taking it extremely seriously. So much so that I’ve been building a tool to help me optimize and monitor the sites that I build to make sure that I’m making an attempt to offer the best experience to those who visit them. If you’re into performant, accessible and SEO friendly sites, you might like it too! You can check it out at Optimize Toolset.

About

Hi, 👋, I’m Ryan Hefner  and I built this site for me, and you! The goal of this site was to provide an easy way for me to check the stats on my npm packages, both for prioritizing issues and updates, and to give me a little kick in the pants to keep up on stuff.

As I was building it, I realized that I was actually using the tool to build the tool, and figured I might as well put this out there and hopefully others will find it to be a fast and useful way to search and browse npm packages as I have.

If you’re interested in other things I’m working on, follow me on Twitter or check out the open source projects I’ve been publishing on GitHub.

I am also working on a Twitter bot for this site to tweet the most popular, newest, random packages from npm. Please follow that account now and it will start sending out packages soon–ish.

Open Software & Tools

This site wouldn’t be possible without the immense generosity and tireless efforts from the people who make contributions to the world and share their work via open source initiatives. Thank you 🙏

© 2025 – Pkg Stats / Ryan Hefner

is-check

v1.0.2

Published

Check if the given value is of a specific type.

Vulnerabilities

Powered byPowered by Snyk
  • 0High
  • 0Medium
  • 0Low

Links

Git

Maintainers

pmatzavinpmatzavin

Keywords

checktypetypeofisArrayisNumberisObjectisNullisUndefinedisNilisBooleanisStringarraynumberobjectnullundefinednilbooleanstring

Readme

is-check

Check if the given value is of a specific type.

About

Provide a simple and clean way to check if a value matches a specific type. Abstract the usage of "typeof === '...'".

Installation

npm install is-check

Module Usage

var check = require('is-check');
var myValue = 'something';
check.isArray(myValue);
check.isBoolean(myValue);
check.isFunction(myValue);
check.isNil(myValue);
check.isNull(myValue);
check.isNumber(myValue);
check.isObject(myValue);
check.isString(myValue);
check.isUndefined(myValue);

Running the tests

From inside the root project folder run:

npm install

and then if you are on a windows machine:

npm test

if you are on a unix machine:

npm testUNIX

Spec

TOC

function isArray()

returns true:

isArray([]) should be true.

check.isArray([]).should.be.ok;

isArray([1]) should be true.

check.isArray([1]).should.be.ok;

isArray([new Array()]) should be true.

check.isArray([new Array()]).should.be.ok;

isArray([Array.prototype]) should be true.

check.isArray([Array.prototype]).should.be.ok;

returns false:

isArray(37) should be false.

check.isArray(37).should.not.be.ok;

isArray(3.14) should be false.

check.isArray(3.14).should.not.be.ok;

isArray(Math.LN2) should be false.

check.isArray(Math.LN2).should.not.be.ok;

isArray(Infinity) should be false.

check.isArray(Infinity).should.not.be.ok;

isArray(Number(1)) should be false.

check.isArray(Number(1)).should.not.be.ok;

isArray(NaN) should be false.

check.isArray(NaN).should.not.be.ok;

isArray("") should be false.

check.isArray("").should.not.be.ok;

isArray("bla") should be false.

check.isArray("bla").should.not.be.ok;

isArray(typeof 1) should be false.

check.isArray(typeof 1).should.not.be.ok;

isArray("abc") should be false.

check.isArray("abc").should.not.be.ok;

isArray(false) should be false.

check.isArray(false).should.not.be.ok;

isArray(false) should be false.

check.isArray(false).should.not.be.ok;

isArray(Boolean(false)) should be false.

check.isArray(Boolean(false)).should.not.be.ok;

isArray(Boolean(false)) should be false.

check.isArray(Boolean(false)).should.not.be.ok;

isArray( new Boolean(false)) should be false.

check.isArray(Boolean( new Boolean(false))).should.not.be.ok;

isArray(undefined) should be false.

check.isArray(undefined).should.not.be.ok;

isArray(null) should be false.

check.isArray(null).should.not.be.ok;

isArray({a:1}) should be false.

check.isArray({a:1}).should.not.be.ok;

isArray(new Date()) should be false.

check.isArray(new Date()).should.not.be.ok;

isArray(function(){}) should be false.

check.isArray(function(){}).should.not.be.ok;

isArray(Math.sin) should be false.

check.isArray(Math.sin).should.not.be.ok;

function isBoolean()

returns true:

isBoolean(true) should be true.

check.isBoolean(true).should.be.ok;

isBoolean(false) should be true.

check.isBoolean(false).should.be.ok;

isBoolean(Boolean(true)) should be true.

check.isBoolean(Boolean(true)).should.be.ok;

isBoolean(Boolean(false)) should be true.

check.isBoolean(Boolean(false)).should.be.ok;

returns false:

isBoolean(NaN) should be false.

check.isBoolean(NaN).should.not.be.ok;

isBoolean(undefined) should be false.

check.isBoolean(undefined).should.not.be.ok;

isBoolean(null) should be false.

check.isBoolean(null).should.not.be.ok;

isBoolean({a:1}) should be false.

check.isBoolean({a:1}).should.not.be.ok;

isBoolean(new Date()) should be false.

check.isBoolean(new Date()).should.not.be.ok;

isBoolean(function(){}) should be false.

check.isBoolean(function(){}).should.not.be.ok;

isBoolean(Math.sin) should be false.

check.isBoolean(Math.sin).should.not.be.ok;

isBoolean([1, 2, 4]) should be false.

check.isBoolean([1, 2, 4]).should.not.be.ok;

isBoolean(37) should be false.

check.isBoolean(37).should.not.be.ok;

isBoolean(3.14) should be false.

check.isBoolean(3.14).should.not.be.ok;

isBoolean(Math.LN2) should be false.

check.isBoolean(Math.LN2).should.not.be.ok;

isBoolean(Infinity) should be false.

check.isBoolean(Infinity).should.not.be.ok;

isBoolean(Number(1)) should be false.

check.isBoolean(Number(1)).should.not.be.ok;

isBoolean("") should be false.

check.isBoolean("").should.not.be.ok;

isBoolean("bla") should be false.

check.isBoolean("bla").should.not.be.ok;

isBoolean(typeof 1) should be false.

check.isBoolean(typeof 1).should.not.be.ok;

isBoolean("abc") should be false.

check.isBoolean("abc").should.not.be.ok;

function isFunction()

returns true:

isFunction(function(){}) should be true.

check.isFunction(function(){}).should.be.ok;

isFunction(Math.sin) should be true.

check.isFunction(Math.sin).should.be.ok;

returns false:

isFunction(37) should be false.

check.isFunction(37).should.not.be.ok;

isFunction(3.14) should be false.

check.isFunction(3.14).should.not.be.ok;

isFunction(Math.LN2) should be false.

check.isFunction(Math.LN2).should.not.be.ok;

isFunction(Infinity) should be false.

check.isFunction(Infinity).should.not.be.ok;

isFunction(Number(1)) should be false.

check.isFunction(Number(1)).should.not.be.ok;

isFunction(NaN) should be false.

check.isFunction(NaN).should.not.be.ok;

isFunction("") should be false.

check.isFunction("").should.not.be.ok;

isFunction("bla") should be false.

check.isFunction("bla").should.not.be.ok;

isFunction(typeof 1) should be false.

check.isFunction(typeof 1).should.not.be.ok;

isFunction("abc") should be false.

check.isFunction("abc").should.not.be.ok;

isFunction(true) should be false.

check.isFunction(true).should.not.be.ok;

isFunction(false) should be false.

check.isFunction(false).should.not.be.ok;

isFunction(Boolean(true)) should be false.

check.isFunction(Boolean(true)).should.not.be.ok;

isFunction(Boolean(false)) should be false.

check.isFunction(Boolean(false)).should.not.be.ok;

isFunction( new Boolean(true)) should be false.

check.isFunction(Boolean( new Boolean(true))).should.not.be.ok;

isFunction(undefined) should be false.

check.isFunction(undefined).should.not.be.ok;

isFunction(null) should be false.

check.isFunction(null).should.not.be.ok;

isFunction({a:1}) should be false.

check.isFunction({a:1}).should.not.be.ok;

isFunction(new Date()) should be false.

check.isFunction(new Date()).should.not.be.ok;

isFunction([1, 2, 4]) should be false.

check.isFunction([1, 2, 4]).should.not.be.ok;

function isNill()

returns true:

isNil(null) should be true.

check.isNil(null).should.be.ok;

isNil(undefined) should be true.

check.isNil(undefined).should.be.ok;

returns false:

isNil(NaN) should be false.

check.isNil(NaN).should.not.be.ok;

isNil("") should be false.

check.isNil("").should.not.be.ok;

isNil("bla") should be false.

check.isNil("bla").should.not.be.ok;

isNil(typeof 1) should be false.

check.isNil(typeof 1).should.not.be.ok;

isNil("abc") should be false.

check.isNil("abc").should.not.be.ok;

isNil(true) should be false.

check.isNil(true).should.not.be.ok;

isNil(false) should be false.

check.isNil(false).should.not.be.ok;

isNil(Boolean(true)) should be false.

check.isNil(Boolean(true)).should.not.be.ok;

isNil(Boolean(false)) should be false.

check.isNil(Boolean(false)).should.not.be.ok;

isNil( new Boolean(true)) should be false.

check.isNil(Boolean( new Boolean(true))).should.not.be.ok;

isNil({a:1}) should be false.

check.isNil({a:1}).should.not.be.ok;

isNil(new Date()) should be false.

check.isNil(new Date()).should.not.be.ok;

isNil(function(){}) should be false.

check.isNil(function(){}).should.not.be.ok;

isNil(Math.sin) should be false.

check.isNil(Math.sin).should.not.be.ok;

isNil([1, 2, 4]) should be false.

check.isNil([1, 2, 4]).should.not.be.ok;

isNil(37) should be false.

check.isNil(37).should.not.be.ok;

isNil(3.14) should be false.

check.isNil(3.14).should.not.be.ok;

isNil(Math.LN2) should be false.

check.isNil(Math.LN2).should.not.be.ok;

isNil(Infinity) should be false.

check.isNil(Infinity).should.not.be.ok;

isNil(Number(1)) should be false.

check.isNil(Number(1)).should.not.be.ok;

function isNull()

returns true:

isNull(null) should be true.

check.isNull(null).should.be.ok;

returns false:

isNull(37) should be false.

check.isNull(37).should.not.be.ok;

isNull(3.14) should be false.

check.isNull(3.14).should.not.be.ok;

isNull(Math.LN2) should be false.

check.isNull(Math.LN2).should.not.be.ok;

isNull(Infinity) should be false.

check.isNull(Infinity).should.not.be.ok;

isNull(Number(1)) should be false.

check.isNull(Number(1)).should.not.be.ok;

isNull(NaN) should be false.

check.isNull(NaN).should.not.be.ok;

isNull("") should be false.

check.isNull("").should.not.be.ok;

isNull("bla") should be false.

check.isNull("bla").should.not.be.ok;

isNull(typeof 1) should be false.

check.isNull(typeof 1).should.not.be.ok;

isNull("abc") should be false.

check.isNull("abc").should.not.be.ok;

isNull(true) should be false.

check.isNull(true).should.not.be.ok;

isNull(false) should be false.

check.isNull(false).should.not.be.ok;

isNull(Boolean(true)) should be false.

check.isNull(Boolean(true)).should.not.be.ok;

isNull(Boolean(false)) should be false.

check.isNull(Boolean(false)).should.not.be.ok;

isNull( new Boolean(true)) should be false.

check.isNull(Boolean( new Boolean(true))).should.not.be.ok;

isNull(undefined) should be false.

check.isNull(undefined).should.not.be.ok;

isNull({a:1}) should be false.

check.isNull({a:1}).should.not.be.ok;

isNull(new Date()) should be false.

check.isNull(new Date()).should.not.be.ok;

isNull(function(){}) should be false.

check.isNull(function(){}).should.not.be.ok;

isNull(Math.sin) should be false.

check.isNull(Math.sin).should.not.be.ok;

isNull([1, 2, 4]) should be false.

check.isNull([1, 2, 4]).should.not.be.ok;

function isNumber()

returns true:

isNumber(37) should be true.

check.isNumber(37).should.be.ok;

isNumber(3.14) should be true.

check.isNumber(3.14).should.be.ok;

isNumber(Math.LN2) should be true.

check.isNumber(Math.LN2).should.be.ok;

isNumber(Infinity) should be true.

check.isNumber(Infinity).should.be.ok;

isNumber(Number(1)) should be true.

check.isNumber(Number(1)).should.be.ok;

returns false:

isNumber(NaN) should be false.

check.isNumber(NaN).should.not.be.ok;

isNumber("") should be false.

check.isNumber("").should.not.be.ok;

isNumber("bla") should be false.

check.isNumber("bla").should.not.be.ok;

isNumber(typeof 1) should be false.

check.isNumber(typeof 1).should.not.be.ok;

isNumber("abc") should be false.

check.isNumber("abc").should.not.be.ok;

isNumber(true) should be false.

check.isNumber(true).should.not.be.ok;

isNumber(false) should be false.

check.isNumber(false).should.not.be.ok;

isNumber(Boolean(true)) should be false.

check.isNumber(Boolean(true)).should.not.be.ok;

isNumber(Boolean(false)) should be false.

check.isNumber(Boolean(false)).should.not.be.ok;

isNumber( new Boolean(true)) should be false.

check.isNumber(Boolean( new Boolean(true))).should.not.be.ok;

isNumber(undefined) should be false.

check.isNumber(undefined).should.not.be.ok;

isNumber(null) should be false.

check.isNumber(null).should.not.be.ok;

isNumber({a:1}) should be false.

check.isNumber({a:1}).should.not.be.ok;

isNumber(new Date()) should be false.

check.isNumber(new Date()).should.not.be.ok;

isNumber(function(){}) should be false.

check.isNumber(function(){}).should.not.be.ok;

isNumber(Math.sin) should be false.

check.isNumber(Math.sin).should.not.be.ok;

isNumber([1, 2, 4]) should be false.

check.isNumber([1, 2, 4]).should.not.be.ok;

function isObject()

returns true:

isObject({a:1}) should be true.

check.isObject({a:1}).should.be.ok;

isObject(new Date()) should be true.

check.isObject(new Date()).should.be.ok;

isObject(new Boolean(true)) should be true.

check.isObject(new Boolean(true)).should.be.ok;

returns false:

isObject(37) should be false.

check.isObject(37).should.not.be.ok;

isObject(3.14) should be false.

check.isObject(3.14).should.not.be.ok;

isObject(Math.LN2) should be false.

check.isObject(Math.LN2).should.not.be.ok;

isObject(Infinity) should be false.

check.isObject(Infinity).should.not.be.ok;

isObject(Number(1)) should be false.

check.isObject(Number(1)).should.not.be.ok;

isObject(NaN) should be false.

check.isObject(NaN).should.not.be.ok;

isObject("") should be false.

check.isObject("").should.not.be.ok;

isObject("bla") should be false.

check.isObject("bla").should.not.be.ok;

isObject(typeof 1) should be false.

check.isObject(typeof 1).should.not.be.ok;

isObject("abc") should be false.

check.isObject("abc").should.not.be.ok;

isObject(true) should be false.

check.isObject(true).should.not.be.ok;

isObject(false) should be false.

check.isObject(false).should.not.be.ok;

isObject(Boolean(true)) should be false.

check.isObject(Boolean(true)).should.not.be.ok;

isObject(Boolean(false)) should be false.

check.isObject(Boolean(false)).should.not.be.ok;

isObject( new Boolean(true)) should be false.

check.isObject(Boolean( new Boolean(true))).should.not.be.ok;

isObject(undefined) should be false.

check.isObject(undefined).should.not.be.ok;

isObject(null) should be false.

check.isObject(null).should.not.be.ok;

isObject(function(){}) should be false.

check.isObject(function(){}).should.not.be.ok;

isObject(Math.sin) should be false.

check.isObject(Math.sin).should.not.be.ok;

isObject([1, 2, 4]) should be false.

check.isObject([1, 2, 4]).should.not.be.ok;

function isString()

returns true:

isString("") should be true.

check.isString("").should.be.ok;

isString("bla") should be true.

check.isString("bla").should.be.ok;

isString(typeof 1) should be true.

check.isString(typeof 1).should.be.ok;

isString("abc") should be true.

check.isString("abc").should.be.ok;

returns false:

isString(NaN) should be false.

check.isString(NaN).should.not.be.ok;

isString(true) should be false.

check.isString(true).should.not.be.ok;

isString(false) should be false.

check.isString(false).should.not.be.ok;

isString(Boolean(true)) should be false.

check.isString(Boolean(true)).should.not.be.ok;

isString(Boolean(false)) should be false.

check.isString(Boolean(false)).should.not.be.ok;

isString( new Boolean(true)) should be false.

check.isString(Boolean( new Boolean(true))).should.not.be.ok;

isString(undefined) should be false.

check.isString(undefined).should.not.be.ok;

isString(null) should be false.

check.isString(null).should.not.be.ok;

isString({a:1}) should be false.

check.isString({a:1}).should.not.be.ok;

isString(new Date()) should be false.

check.isString(new Date()).should.not.be.ok;

isString(function(){}) should be false.

check.isString(function(){}).should.not.be.ok;

isString(Math.sin) should be false.

check.isString(Math.sin).should.not.be.ok;

isString([1, 2, 4]) should be false.

check.isString([1, 2, 4]).should.not.be.ok;

isString(37) should be false.

check.isString(37).should.not.be.ok;

isString(3.14) should be false.

check.isString(3.14).should.not.be.ok;

isString(Math.LN2) should be false.

check.isString(Math.LN2).should.not.be.ok;

isString(Infinity) should be false.

check.isString(Infinity).should.not.be.ok;

isString(Number(1)) should be false.

check.isString(Number(1)).should.not.be.ok;

function isUndefined()

returns true:

isUndefined(undefined) should be true.

check.isUndefined(undefined).should.be.ok;

returns false:

isUndefined(37) should be false.

check.isUndefined(37).should.not.be.ok;

isUndefined(3.14) should be falsw.

check.isUndefined(3.14).should.not.be.ok;

isUndefined(Math.LN2) should be false.

check.isUndefined(Math.LN2).should.not.be.ok;

isUndefined(Infinity) should be false.

check.isUndefined(Infinity).should.not.be.ok;

isUndefined(Number(1)) should be false.

check.isUndefined(Number(1)).should.not.be.ok;

isUndefined(NaN) should be false.

check.isUndefined(NaN).should.not.be.ok;

isUndefined("") should be false.

check.isUndefined("").should.not.be.ok;

isUndefined("bla") should be false.

check.isUndefined("bla").should.not.be.ok;

isUndefined(typeof 1) should be false.

check.isUndefined(typeof 1).should.not.be.ok;

isUndefined("abc") should be false.

check.isUndefined("abc").should.not.be.ok;

isUndefined(true) should be false.

check.isUndefined(true).should.not.be.ok;

isUndefined(false) should be false.

check.isUndefined(false).should.not.be.ok;

isUndefined(Boolean(true)) should be false.

check.isUndefined(Boolean(true)).should.not.be.ok;

isUndefined(Boolean(false)) should be false.

check.isUndefined(Boolean(false)).should.not.be.ok;

isUndefined( new Boolean(true)) should be false.

check.isUndefined(Boolean( new Boolean(true))).should.not.be.ok;

isUndefined(null) should be false.

check.isUndefined(null).should.not.be.ok;

isUndefined({a:1}) should be false.

check.isUndefined({a:1}).should.not.be.ok;

isUndefined(new Date()) should be false.

check.isUndefined(new Date()).should.not.be.ok;

isUndefined(function(){}) should be false.

check.isUndefined(function(){}).should.not.be.ok;

isUndefined(Math.sin) should be false.

check.isUndefined(Math.sin).should.not.be.ok;

isUndefined([1, 2, 4]) should be false.

check.isUndefined([1, 2, 4]).should.not.be.ok;