fdaciuk/is

# is

> Typechecker in Vanilla JS

[![Build Status][travis-image]][travis-url]
[![Coveralls Coverage Status][coverage-image]][coverage-url]
[![Code Climate Coverage][codeclimate-coverage-image]][codeclimate-coverage-url]
[![Code Climate][codeclimate-image]][codeclimate-url]
[![License][license-image]][license-url]
[![CONTRIBUTING][contributing-image]][contributing-url]

## Why?

Because type checking in JS is hard. See some examples:

```js
console.log(typeof 1) // 'number'
console.log(typeof 'javascript') // 'string'
console.log(typeof {}) // 'object'
console.log(typeof []) // 'object' wat?
console.log(typeof null) // 'object' wat? wat?
console.log(typeof new String('js')) // 'object' :|
```

That's why `@fdaciuk/is` is useful. See some examples using this library in ES2015:

```js
import is from '@fdaciuk/is'

console.log(is('number', 10)) // true
console.log(is('object', {})) // true
console.log(is('array', [])) // true
console.log(is('object', [])) // false
console.log(is('string', new String('js'))) // true (yes, 'string', not 'object')
```

## Installation

**Yarn**

```console
yarn add @fdaciuk/is
```

**NPM**

```console
npm i --save @fdaciuk/is
```

## Usage

**AMD**

```js
define(['is'], function (is) {
  console.log(is('arguments', arguments)) // true
})
```

**CommonJS**

```js
var is = require('@fdaciuk/is').default
console.log(is('array', [])) // true
```

**ES6 / ES2015 Module**

```js
import is from '@fdaciuk/is'

const isString = is('string')
console.log(isString('daciuk')) // true
```

**Method of `window` object**

```js
console.log(window.is('number', 10)) // true
```

## Signature

```js
is(typeToTest, value)
// or
is(typeToTest)(value)
```

## Documentation

**`is`**

A function that checks if a value is of a type:

```js
import is from '@fdaciuk/is'
// or using commonjs:
// var is = require('@fdaciuk/is').default

const value = []

if (is('array', value)) {
  // do something
}
```

**`typeOf`**

A function that returns a real type of a value:

```js
import { typeOf } from '@fdaciuk/is'
// or using commonjs:
// var typeOf = require('@fdaciuk/is').typeOf

console.log(typeOf([])) // 'array'
console.log(typeOf(123)) // 'number'
console.log(typeOf(new String('hey'))) // 'string', not 'object'
```

## Contributing

Check [CONTRIBUTING.md](contributing-url)

## License

[MIT](license-url) © Fernando Daciuk

[travis-image]: https://img.shields.io/travis/fdaciuk/is.svg?style=flat-square
[travis-url]: https://travis-ci.org/fdaciuk/is
[coverage-image]: https://img.shields.io/coveralls/fdaciuk/is/master.svg?style=flat-square
[coverage-url]: https://coveralls.io/r/fdaciuk/is?branch=master
[codeclimate-coverage-image]: https://img.shields.io/codeclimate/coverage/github/fdaciuk/is.svg?style=flat-square
[codeclimate-coverage-url]: https://codeclimate.com/github/fdaciuk/is
[codeclimate-image]: https://img.shields.io/codeclimate/github/fdaciuk/is.svg?style=flat-square
[codeclimate-url]: https://codeclimate.com/github/fdaciuk/is
[license-image]: https://img.shields.io/badge/license-MIT-blue.svg?style=flat-square
[license-url]: https://github.com/fdaciuk/licenses/blob/master/MIT-LICENSE.md
[contributing-image]: https://img.shields.io/badge/fdaciuk%2Fis-CONTRIBUTE-orange.svg?style=flat-square
[contributing-url]: CONTRIBUTING.md