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 |

Specific Checks

is.nan is only true if passed in NaN. is.undefined is only true if passed in undefined.

Testing

npm install -g mocha
npm test

License

MIT