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<h1>Extract Options & Callback</h1>
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<!-- DESCRIPTION/ -->
Extract the options and callback from a function's arguments easily
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<!-- INSTALL/ -->
<h2>Install</h2>
<a href="https://npmjs.com" title="npm is a package manager for javascript"><h3>NPM</h3></a><ul>
<li>Install: <code>npm install --save extract-opts</code></li>
<li>Module: <code>require('extract-opts')</code></li></ul>
<a href="http://browserify.org" title="Browserify lets you require('modules') in the browser by bundling up all of your dependencies"><h3>Browserify</h3></a><ul>
<li>Install: <code>npm install --save extract-opts</code></li>
<li>Module: <code>require('extract-opts')</code></li>
<li>CDN URL: <code>//wzrd.in/bundle/extract-opts@3.3.1</code></li></ul>
<a href="http://enderjs.com" title="Ender is a full featured package manager for your browser"><h3>Ender</h3></a><ul>
<li>Install: <code>ender add extract-opts</code></li>
<li>Module: <code>require('extract-opts')</code></li></ul>
<h3><a href="https://github.com/bevry/editions" title="Editions are the best way to produce and consume packages you care about.">Editions</a></h3>
<p>This package is published with the following editions:</p>
<ul><li><code>extract-opts</code> aliases <code>extract-opts/index.js</code> which uses <a href="https://github.com/bevry/editions" title="Editions are the best way to produce and consume packages you care about.">Editions</a> to automatically select the correct edition for the consumers environment</li>
<li><code>extract-opts/source/index.js</code> is Source + <a href="https://babeljs.io/docs/learn-es2015/" title="ECMAScript Next">ESNext</a> + <a href="https://nodejs.org/dist/latest-v5.x/docs/api/modules.html" title="Node/CJS Modules">Require</a></li>
<li><code>extract-opts/es2015/index.js</code> is <a href="https://babeljs.io" title="The compiler for writing next generation JavaScript">Babel</a> Compiled + <a href="http://babeljs.io/docs/plugins/preset-es2015/" title="ECMAScript 2015">ES2015</a> + <a href="https://nodejs.org/dist/latest-v5.x/docs/api/modules.html" title="Node/CJS Modules">Require</a></li></ul>
<p>Older environments may need <a href="https://babeljs.io/docs/usage/polyfill/" title="A polyfill that emulates missing ECMAScript environment features">Babel's Polyfill</a> or something similar.</p>
<!-- /INSTALL -->
## Usage
``` javascript
var log = console.log.bind(console)
var extractOptsAndCallback = require('extract-opts')
// fs.readFile(filename, [options], callback)
function readFile (filename, opts, next) {
// Extract options and callback
var args = extractOptsAndCallback(opts, next)
opts = args[0]
next = args[1]
// Forward for simplicities sake
require('fs').readFile(filename, opts, next)
}
// Test it
readFile('package.json', log) // works with no options
readFile('package.json', null, log) // works with null options
readFile('package.json', {next: log}) // works with just options
```
### Customisation
Extract Options and Callback also supports a third argument.
You can use this third argument to customize the `completionCallbackNames` property that defaults to `['next']`.
This is useful if your completion callback has other names besides `next`.
Allowing you to do the following:
``` javascript
var log = console.log.bind(console)
function extractOptsAndCallback (opts, next, config) {
if ( config == null ) config = {}
if ( config.completionCallbackNames == null ) config.completionCallbackNames = ['next', 'complete', 'done']
return require('extract-opts')(opts, next, config)
}
# The readFile method as before
# Test it
readFile('package.json', {next: log}) # works the standard completion callback name
readFile('package.json', {complete: log}) # works with our custom completion callback name
readFile('package.json', {done: log}) # works with our custom completion callback name
```
<!-- HISTORY/ -->
<h2>History</h2>
<a href="https://github.com/bevry/extract-opts/blob/master/HISTORY.md#files">Discover the release history by heading on over to the <code>HISTORY.md</code> file.</a>
<!-- /HISTORY -->
<!-- CONTRIBUTE/ -->
<h2>Contribute</h2>
<a href="https://github.com/bevry/extract-opts/blob/master/CONTRIBUTING.md#files">Discover how you can contribute by heading on over to the <code>CONTRIBUTING.md</code> file.</a>
<!-- /CONTRIBUTE -->
<!-- BACKERS/ -->
<h2>Backers</h2>
<h3>Maintainers</h3>
These amazing people are maintaining this project:
<ul><li><a href="https://balupton.com">Benjamin Lupton</a> — <a href="https://github.com/bevry/extract-opts/commits?author=balupton" title="View the GitHub contributions of Benjamin Lupton on repository bevry/extract-opts">view contributions</a></li></ul>
<h3>Sponsors</h3>
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