Neologistic Paraphasic Mumbling
Miss any of our Open RFC calls?Watch the recordings here! »


1.2.0 • Public • Published

The easiest and most powerful type checking node.js package yet! Did I mention it has powerful plugin support?


npm i --save typecheckjs


The core plugin will recognize NaN, String, Number, Boolean, Function, Array, Object, and every constructor function (like Date). Use it like this:

const type = require('typecheckjs')

type(Number).is(1) // true
type(String).is(1) // true

type(Date).is(new Date()) // true

type(Number).is(NaN) // true
type(NaN).is(NaN)    // true
type(NaN).is(1)      // false

If you want to accept multiple types, you can do so:

type(Number).or(String).is(1)    // true
type(Number).or(String).is('a')  // true
type(Number).or(String).is(true) // false

It is also possible to check the contents of an array or object:

type(Array).of(Number).is([1,2,3]) // true
type(Array).of(Number).is([1,'a']) // false

type(Object).of(Number).is({a:1}) // true

type(Object).of({a: Number, b: String}).is({a: 1, b: 'b'}) //true
type(Array).of([Number, String]).is([1, 'a']) // true

Check the tests in the repo for more info: link


typecheckjs contains a well-crafted plugin system that enables developers with specific needs to easily code for type safety.

To use it in your code, first import the library and the plugins you would like to use. Then configure typecheckjs to make use of them:

const Immutable = require('immutable')
const Type = require('typecheckjs')
const immutableplugin = require('typecheckjsimmutable') // In development

const type = Type.withPlugins([immutableplugin])

Now you can use whatever tests this plugin provides, for example:

let map = Immutable.Map({a: 10})
type(Immutable.Map).of(Number).is(map) // true

To develop a plugin, refer to


npm i typecheckjs

DownloadsWeekly Downloads






Last publish


  • avatar