argx

argx
==========

[![Build Status][bd_travis_shield_url]][bd_travis_url]
[![npm Version][bd_npm_shield_url]][bd_npm_url]
[![JS Standard][bd_standard_shield_url]][bd_standard_url]

[bd_repo_url]: https://github.com/okunishinishi/node-argx
[bd_travis_url]: http://travis-ci.org/okunishinishi/node-argx
[bd_travis_shield_url]: http://img.shields.io/travis/okunishinishi/node-argx.svg?style=flat
[bd_travis_com_url]: http://travis-ci.com/okunishinishi/node-argx
[bd_travis_com_shield_url]: https://api.travis-ci.com/okunishinishi/node-argx.svg?token=
[bd_license_url]: https://github.com/okunishinishi/node-argx/blob/master/LICENSE
[bd_codeclimate_url]: http://codeclimate.com/github/okunishinishi/node-argx
[bd_codeclimate_shield_url]: http://img.shields.io/codeclimate/github/okunishinishi/node-argx.svg?style=flat
[bd_codeclimate_coverage_shield_url]: http://img.shields.io/codeclimate/coverage/github/okunishinishi/node-argx.svg?style=flat
[bd_gemnasium_url]: https://gemnasium.com/okunishinishi/node-argx
[bd_gemnasium_shield_url]: https://gemnasium.com/okunishinishi/node-argx.svg
[bd_npm_url]: http://www.npmjs.org/package/argx
[bd_npm_shield_url]: http://img.shields.io/npm/v/argx.svg?style=flat
[bd_standard_url]: http://standardjs.com/
[bd_standard_shield_url]: https://img.shields.io/badge/code%20style-standard-brightgreen.svg

Parse function arguments. Useful to implement variadic functions.

Installation
-----

``bash
npm install argx --save
`

Usage
-----

Pass the arguments object to .argx() inside your function.

`javascript
/**
* This is an example to declare an variadic functions.
*/
'use strict'

const argx = require('argx')

function doSomething (values, options, callback) {
let args = argx(arguments)
callback = args.pop('function') || function noop () {} // Consume last argument if it's a function.
options = args.pop('object') || {} // Consume last argument if it's an object.
values = args.remain() // Get remaining arguments as array.
/ ... /
}

doSomething('foo', 'bar')
doSomething('foo', 'bar', { verbose: true })
doSomething('foo', 'bar', (err) => {})
doSomething('foo', 'bar', { verbose: true }, (err) => {})

``

API Guide
-----

API guide for Argx instance, which is returned by argx(arguments).

| Signature | Description | Example
| ----- | ----- | --- |
| .pop() | Pop an argument value from last. | args.pop() |
| .pop(count) | Pop multiple values from last. Orders are preserved. | args.pop(1) |
| .pop(type) | Pop only if the last value conform the type. | args.pop("number")
args.pop("number|string")
args.pop(CustomObj) |
| .pop(count, type) | Pop values while conforming the type. | args.pop(2, "number")
args.pop(1, CustomObj) |
| .shift() | Shift an argument value from top. | args.shift() |
| .shift(count) | Shift multiple values from top. | args.shift(2) |
| .shift(type) | Shift only if the top value conform the type. | args.shift("string")
args.pop("object|string")
args.shift(CustomObj) |
| .shift(count, type) | Shift values while conforming the type. | args.shift(2, "string")
args.shift(4, CustomObj) |
| .remain() | Shift all remained values. Always returns an array. | args.remain() |

Tips
-----

$3

Type which .pop()/.shift() accept is string, a custom object or a custom constructor.

`javascript
function MyConstructor(){/.../};
args.pop(MyConstructor); // Pop only if the last argument is instantiate by new MyConstructor()

var MyObj = {/.../};
args.pop(MyObj); // Pop only if the last argument is create by Object.create(MyObj)
`

$3

There are two ways to specify 'or' condition for types.

1. Passing string joined by "|" (eg: args.pop('string|number'); )
2. Passing array as type (eg: args.pop(['string', MyCustomObj]); )

$3

Note that .pop()/.shift() methods returns values as array only when multiple entries hit.
If you want to make sure to keep values as array, use [].concat().

`javascript
var args = argx(arguments);
var values = [].concat(args.pop(2, 'string') || []); // Always array.
``

License
-------
This software is released under the MIT License.