JSPM

Check if argv has a specific flag

Check if something is a Node.js stream

Get the native type of a value.

Check if the character represented by a given Unicode code point is fullwidth

Returns true if a number or string value is a finite number. Useful for regex matches, parsing, user input, etc.

Check if a path is a file, directory, or symlink

Returns `true` if the given string looks like a glob pattern or an extglob pattern. This makes it easy to create code that only uses external modules like node-glob when necessary, resulting in much faster code execution and initialization time, and a bet

Check if the process is running inside Windows Subsystem for Linux (Bash on Windows)

Returns true if the value is an object and not an array or null.

Returns true if a string has an extglob.

Check if a value is a plain object

type-check allows you to check the types of JavaScript values at runtime with a Haskell like type syntax.

Check if a file path is a binary file

Detect the file type of a file, stream, or data

Returns true if an object was created by the `Object` constructor, or Object.create(null).

Check if something is a generator function

Returns true if a value is a plain object, array or function.

Detect whether the terminal supports Unicode

Returns true if the platform is windows. UMD module, works with node.js, commonjs, browser, AMD, electron, etc.

Returns true if a value has the characteristics of a valid JavaScript descriptor. Works for data descriptors and accessor descriptors.

Check if a value is an object

Type check values

Returns true if a value has the characteristics of a valid JavaScript accessor descriptor.

Returns true if a value has the characteristics of a valid JavaScript data descriptor.

unist utility to check if a node passes a test

Returns true if a value exists, false if empty. Works with deeply nested values using object paths.

Detect whether a terminal supports hyperlinks

Runtime library to validate data against TypeScript interfaces

unist utility to recursively walk over nodes, with ancestral information

Check which JavaScript environment your code is running in at runtime: browser, Node.js, Bun, etc

Check if your package was installed globally

Lint files staged by git

Check if a path is the current working directory

Check if your code is running as an npm script

Check if a value is a regular expression

micromark extension to support GFM task list items

Returns `true` if the path appears to be relative.

Check if a string matches the name of a Node.js builtin module

Isomorphic, functional type-checking for Javascript

Check whether a request can be retried based on the `error.code`

Returns true if a file path is absolute. Does not rely on the path module and can be used as a polyfill for node.js native `path.isAbolute`.

Check if a URL is absolute

Update notifications for your CLI app

Check if a file path is a text file

mdast extension to parse and serialize GFM task list items

Check if something is a promise

Check if a value is a Fetch network error

Check if a path is in the current working directory

JavaScript Standard Style - ESLint Shareable Config

A little library for asserting types and values, with zero dependencies.

Displays a beginner-friendly message telling your user to upgrade their version of Node

A simple and composable way to validate data in JavaScript (and TypeScript).

Check if a value is a natural number

Returns `true` if the value is a primitive.

Check if an input value is a ssh url or not.

A straightforward implementation of base58-check encoding

Check if a Buffer/Uint8Array is a GZIP file

Coalesce for JavaScript. Returns the first value that is not undefined or null.

Detect which package manager you're using (yarn or npm)

Check if a module ID is resolvable with require()

Return true if a value is a valid glob pattern or patterns.

A simple Node.js module to check if a TCP port is already bound.

Check if a string is a URL

Check if a number is a redirect HTTP status code

Returns true if a windows file path has invalid characters.

Typescript-compatible minimalistic shallow equality check for arrays/objects

Check if a local or remote port is reachable

URI validation functions

Check if a value is an Observable

Drop-in replacement for `fs.existsSync` with zero dependencies. Other libs I found either have crucial differences from fs.existsSync, or unnecessary dependencies. See README.md for more info.

Get the operating system CPU architecture

Detect the archive type of a Buffer/Uint8Array

Check whether operating system CPU architecture is 64-bit or 32-bit (Supports browsers)

A type checking library where each exported function returns either true or false and does not throw. Also added tests.

Check if a binary is working

Binary wrapper that makes your programs seamlessly available as local dependencies

Check if a string is SVG

Returns true if a file path does not contain any invalid characters.

Hook and modify stdout and stderr

hast utility to check if a node has a property

Check if a string is an IP address

Type assertions aka less-broken `typeof`

`util.inspect` with additional type information

Check if the process is running in a Continuous Integration (CI) environment

Determine if a filename and/or buffer is text or binary. Smarter detection than the other solutions.

Check if a binary is working

Detect the archive type of a Buffer/Uint8Array

Check dependencies in your node module

Validates if a value is an array.

Match BCP 47 language tags with language ranges per RFC 4647

A tiny javascript type testing tool

JavaScript Standard Style JSX support - ESLint Shareable Config

Validates if a value is a number.

Returns true if the value passed is all whitespace.

Binary wrapper that makes your programs seamlessly available as local dependencies

Validates if a value is an integer.

Function argument validation for humans

Checks if the given value is a window object.

Check if a Buffer/Uint8Array is a PNG image

find undeclared identifiers and property accesses in a javascript file.

Check if a string only contains alphanumeric characters

Returns `true` if an array has a glob pattern.

Check if a Buffer/Uint8Array is a JPEG image

Validate an email address according to RFCs 5321, 5322, and others

Binary wrapper that makes your programs seamlessly available as local dependencies

Update notifications for your CLI app, maintained in CommonJS (CJS)

Check whether a value is "empty".

Check if mobile browser.

Binary wrapper for Flow - A static type checker for JavaScript

JavaScript Standard Style

Ensure a path doesn't contain null bytes

Wrap your standards in a tortilla and cover it in special sauce.

Test if an object has a specified property.

ESLint shareable config for the Google style

Test if a value is an array.

Return a function which tests if every element in an array passes a test condition.

Determine the name of a value's constructor.

Check if a Buffer/Uint8Array is a GIF image

Validate domain name

Test if a value is object-like.

Check whether a RegExp flag is supported

ESLint shareable config for XO

Check if an environment is big endian.

Test if a double-precision floating-point numeric value is infinite.

Check if a URL is relative

Check if a string is HTML

maximally minimal type-testing library

Test if a double-precision floating-point numeric value is NaN.

Test if a value is a regular expression string.

Test if a value is a regular expression.

Try to downgrade the permissions of a process with root privileges and block access if it fails

Test if a value is an object.

Test if a value is a string.

JavaScript/TypeScript linter (ESLint wrapper) with great defaults

Test if a value is a Float32Array.

Test if a value is a number.

Determine a value's type.

Determine the specification defined classification of an object.

Test if a value is a boolean.

Test if a value is a function.

A simple and composable way to validate data in JavaScript (and TypeScript).

Test if a value is a Float64Array.

Test whether a path exists on the filesystem.

Test if a value is a Uint32Array.

Test if a value is a Buffer object.

check if an AST node is a function of some sort

Test if a value is a Uint8Array.

Test if a value is a Uint16Array.

Test if a value is a plain object.

Check for outdated, incorrect, and unused dependencies.

Get a property from an object using dot (object path) notation.

Tiny wrapper around ansi-colors to add colored symbols and a timestamp.

Check if an environment is little endian.

Check if a Buffer/Uint8Array is a TAR file

Is this a bluebird promise I see before me?

Check if a process is running

Check TypeScript type definitions

Check if browser is Internet Explorer

Detect potential issues with users system that could prevent Yeoman from working correctly

Check if a value is a `Blob`

Utilities to get and check variable types (isString, isPlainObject, isRegExp, etc)

Check if browser is Firefox

Is given string a language code (as per IANA)

Check whether a binary exists in the PATH environment variable

check if the current node version has async_hooks.

Promisified version of node-which

ESLint shareable config for TypeScript to be used with eslint-config-xo

Determine if an array or object is equivalent with another, *not* recursively

Verify if something is a Promise

Checks TypeScript types match expected values

Detect the audio type of a Buffer/Uint8Array

Check if Electron is running in development

Checks if a given object is iterable

Checks if the given value is null or undefined

Returns true if the given is falsey (according to JavaScript) or matches a 'falsey' keyword.

check if an AST node is a MemberExpression, in general or a specific one

Check if a string is an IP address

Checks if the given value is a native function.

Reshape into a better npm audit for the community and encourage more people to include security audit into their process.

Check if a string is a valid JavaScript identifier

Check if a Buffer/Uint8Array is a ZIP file

A JSON fixer

A gulp plugin for processing files with ESLint

Looks up the first non-whitespace character to the left/right of a given index

Check whether a package or organization name is available on npm

3x as fast as `is-whitespace` and `whitespace-regex` thanks to `is-string-blank`. This package is a simple function that accepts an argument and returns `true` if it is a string AND it is not blank. Supports Node and Browser environments.

Utils to deal with TCP ports and hostnames. Safe for everyday use.

Keep watch of your bundle size

JavaScript Standard Style React/JSX support - ESLint Shareable Config

A TypeScript ESLint config that loves you

Check if a value is a function

Check if a directory is empty.

Parse dotenv files for Boolean, Array, and Number variable types, built for CrocodileJS

Ember CLI addon for detecting missing npm and bower dependencies before executing ember commands

A proxy to `path`, replacing `\` with `/` for all results

checks whether a hyperlink is alive (200 OK) or dead

Check if a Node.js Buffer or Uint8Array is UTF-8

checks the all of the hyperlinks in a markdown text to determine if they are alive or dead

Detect the image type of an ArrayBuffer/Uint8Array

JavaScript Semistandard Style - ESLint Shareable Config

ESLint shareable config for React to be used with eslint-config-xo

ESLint shareable config for XO with 2-space indent

Validates password according to flexible and intuitive specifications

Check if a Buffer/Uint8Array is a BZIP2 file

Check if a string is a valid filename

Test if a finite numeric value is an odd number.

Aids humans and automation in managing npm audit results

Checks for URLs during typing and pasting and automatically converts them to links.

Keep your library size in check

allows easy type enforcement for all JS types objects and classes. it is also extensible and provides simple to use type checks for your own custom classes and types

is-iojs determines if runtime is io.js.

Returns true if an object has an own, nested property using dot notation paths ('a.b.c').

Context menu for your Electron app

Check the validity of the format of an EU VAT number

Check if an object is an array or a typed array

A collection of functions for working with different casings.

Test if a finite double-precision floating-point number is an integer.

Validate hostname based on RFC-1123

Check if the machine is running Windows or not.

Check whether a binary version satisfies a semver range

Test if a double-precision floating-point numeric value is positive zero.

Test if a value is NaN.

Returns `true` if a value exists in the given string, array or object.

Markdown TaskList components

Hunspell compatible spell checker

TypeScript Standard Style based on StandardJS

Check if the process is running as administrator on Windows

Check if the package is being installed by another package

Test if a value is a number having an integer value.

TypeScript / JavaScript library for detect WebAssembly features in node.js & browser

Test if a value is an Int32Array.

Test if an object's own property is enumerable.

Test if a value is an Int16Array.

Test if a finite numeric value is an even number.

Assert a given object is a valid glob option

Check if a value is undefined or not.

Test if a value is a Uint8ClampedArray.

Test if a value is a number having a nonnegative integer value.

Checks that given package is installed globally or locally.

Detect the appearance of an element in the browser DOM

All the goodness of `feross/standard` with semicolons sprinkled on top.

$(document).ready() for the 21st century

A pure css library to beautify checkbox and radio buttons.

Async npm module for Node JS that reads the first line of a file

Check if the user is running the latest version of the app

code > prettier > stylelint > formatted code

A command line utility to read version from package.json and attach it into your module as a property

Test if a double-precision floating-point numeric value is negative zero.

Returns true if the current node version matches the given semver expression

Test if a value is a collection.