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0.4.0 • Public • Published


This module has been deprecated. You should lock your version to 0.3.3. It will be replaced by a different module.


Convenient high-performance type-checking for JavaScript

value is designed to ease type-checking in JavaScript while keeping performance in mind. It comes with a fluent api to improve the readability of your code. Use value to sanitize function parameters and to provide better error messages if some type is unexpected.

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npm install value@0.3.3

**It's important to use this version number because newer versions will be an entire

If you're not using a CommonJS-system in the browser value is namespaced under window.jhnns.value.


var value = require("value");
// value takes every possible type in JavaScript
// and provides some methods to test for the type.
value(undefined).typeOf(Object); // = false
value(null).typeOf(Object); // = false
value([]).typeOf(Array); // = true
value([]).typeOf(Object); // = false
value(2).typeOf(Number); // = true
value(new String("hello")).typeOf(String); // = true
value(new String("hello")).typeOf(Object); // = false
value(/myRegExp/).typeOf(RegExp); // = true
value(document.createElement("a")).typeOf(HTMLAnchorElement); // = true
// value also provides a negation for better readability
value(2).notTypeOf(String); // = true
// you can also check conveniently for null and undefined with one call
value(undefined).isSet(); // = false
value(null).isNotSet(); // = true
// value also supports convenient type-checking within collections
value([1, 2, 3]).each.typeOf(Number); // = true
value([1, "2", 3]).any.notTypeOf(Number); // = true
value({ one: 1, two: 2, three: null }).any.isNotSet(); // = true


typeOf(constructor): Boolean Alias: instanceOf

Tests if the subject is a child of the constructor. Respects the complete inheritance chain. Keep in mind that everything that is neither null nor undefined is a child of Object (see below).

notTypeOf(constructor): Boolean Alias: notInstanceOf

Negation of typeOf()

isSet(): Boolean

Returns true when the subject is neither null nor undefined

isNotSet(): Boolean

Negation of isSet()

each.typeOf(constructor): Boolean Alias: each.instanceOf

Invokes value(item).typeOf(constructor) on every item within the given collection. Returns true if every item returned true. A collection can be an array or an object.

each.isSet(): Boolean

Invokes the value(item).isSet() on every item within the given collection. Returns true if every item returned true. A collection can be an array or an object.

any.notTypeOf(constructor): Boolean Alias: any.notInstanceOf

Negation of each.typeOf()

any.isNotSet(): Boolean

Negation of each.isSet()

getConstructor(): Function|null

Returns subject.constructor or null if the subject was null or undefined.


value contains a set of opinionated presumptions to avoid common and annoying pitfalls. It has been designed to act like you would expect from a language like ActionScript with optional static types. The returned result is not always conform with the JavaScript type-specification.

This is a collection of cases where value acts differently to the original typeof-operator:

null is not an Object

In contrast to typeof null === "object"

value(null).typeOf(Object); // = false

new String() is a String and not an Object

In constrast to typeof new String() === "object"

value(new String()).typeOf(String); // = true
value(new String()).typeOf(Object); // = false

[] is an Array and not an Object

In constrast to typeof [] === "object"

value([]).typeOf(Object); // = false
value([]).typeOf(Array); // = true

Infinity and NaN are not numbers

In constrast to typeof NaN === "number" and typeof Infinity === "number"

value(NaN).typeOf(Number); // = false
value(Infinity).typeOf(Number); // = false

While NaN and Infinity are numbers from a theoretical point of view it's a common mistake when trying to sanitize calculation parameters. value assumes that numbers are numeric - that's why NaN and Infinity are not numbers.

Please note

arguments !== Array

This stays the same: value(arguments).typeOf(Array) will return false because arguments doesn't provide all methods of Array.



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