Is-simple NPM | npm.io

IS (is-simple)

Quick, easy, and lightweight type checking

Why?

Type checking should be simple. This library does that, in as simple of a way that I can think of. It's easy to get tripped up with some of the neuances of JavaScript (such as typeof null === "object", or isNaN("wtf") === true), and this library aims to prevent that.

Installation

Node.js

npm install is-simple

In the browser

<script src="is.js"/>

Usage

// simple type checking
console.log(is.number(5)); // true
console.log(is.integer(2.5)); // false
console.log(is.function(console.log)); // true

// complex type checking
function Point(x, y) {
    this.x = x;
    this.y = y;
}

var point = new Point(2, 4);
var fakePoint = {x: 2, y: 4};

console.log(is.instanceOf(Point)(p)); // true
console.log(is.instanceOf(Point)(fakePoint)); // false

// even more complex type checking
console.log(is.arrayOf(is.number)([1, 2, 3])); // true
console.log(is.arrayOf(is.instanceOf(Point))([point])); // true

Using your own functions

You can easily extend IS by adding your own functions. These functions can also be passed in to is.arrayOf.

is.even = function (x) {
    return x % 2 === 0;
};

console.log(is.even(4)); // true
console.log(is.arrayOf(is.even)([2, 4, 6, 8])); // true

Matching Basic JavaScript Types

NOTE: typeof null === "object", but IS considers null to not be an object

matches	is.array	is.number	is.boolean	is.string	is.fn	is.object
null, undefined	no	no	no	no	no	no
NaN, Infinity	no	yes	no	no	no	no
0, 2, -5	no	yes	no	no	no	no
0.5, Math.PI	no	yes	no	no	no	no
true, false	no	no	yes	no	no	no
"", "hello"	no	no	no	yes	no	no
[], 1, 2, 3	yes	no	no	no	no	yes
{}	no	no	no	no	no	yes
function () {}, console, window, Object	no	no	no	no	yes	yes

Special Types

NOTE: we treat "" as defined

matches	is.defined	is.realNumber	is.integer
null, undefined	no	no	no
NaN, Infinity	no	no	no
0, 2, -5	yes	yes	yes
0.5, Math.PI	yes	yes	no
true, false	yes	no	no
"", "hello"	yes	no	no
[], 1, 2, 3	yes	no	no
{}	yes	no	no
function () {}, console, window, Object	yes	no	no