.verb.md
# [{%= name %}][author-www-url] [![npmjs.com][npmjs-img]][npmjs-url] [![The MIT License][license-img]][license-url] [![npm downloads][downloads-img]][downloads-url]
> {%= description %}
[![code climate][codeclimate-img]][codeclimate-url] [![standard code style][standard-img]][standard-url] [![travis build status][travis-img]][travis-url] [![coverage status][coveralls-img]][coveralls-url] [![dependency status][david-img]][david-url]
You might also be interested in [hybridify][], [hybridify-all][], [relike-all][], [letta][]
## Install
```
npm i {%= name %} --save
```
## Usage
> For more use-cases see the [tests](./test.js)
```js
const {%= varname %} = require('{%= name %}')
```
**Note:** It treat functions as asynchronous, based on [is-async-function][].
Why you should be aware of that? Because if you give async function which don't have last argument called with some of the [common-callback-names][] it will treat that function as synchronous and things may not work as expected.
It's not a problem for most of the cases and for node's native packages, because that's a convention.
So, the [relike-all][] package successfuly can promisifies all of the `fs` functions for example, except `fs.createReadStream` and `fs.createWriteStream` which is normal.
{%= apidocs('index.js') %}
### .Promise
While `relike` always trying to use native Promise if available in the enviroment, you can
give a Promise constructor to be used on enviroment where there's no support - for example, old
broswers or node's 0.10 version. By default, `relike` will use and include [bluebird][] on old enviroments,
as it is the fastest implementation of Promises. So, you are able to give Promise constructor, but
it won't be used in modern enviroments - it always will use native Promise, you can't trick that. You
can't give custom promise implementation to be used in any enviroment.
**Example**
```js
var fs = require('fs')
var relike = require('relike')
relike.promisify.Promise = require('q') // using `Q` promise on node 0.10
var readFile = relike.promisify(fs.readFile)
readFile('package.json', 'utf8')
.then(console.log, console.error)
```
One way to pass a custom Promise constructor is as shown above. But the other way is passing it to `.Promise` of the promisified function, like that
```js
var fs = require('fs')
var relike = require('relike')
var statFile = relike.promisify(fs.stat)
statFile.Promise = require('when') // using `when` promise on node 0.10
statFile('package.json').then(console.log, console.error)
```
One more thing, is that you can access the used Promise and can detect what promise is used. It is easy, just as `promise.Promise` and you'll get it.
Or look for `promise.___bluebirdPromise` and `promise.___customPromise` properties. `.___bluebirdPromise` (yea, with three underscores in front) will be true if enviroment is old and you didn't provide promise constructor to `.Promise`.
So, when you give constructor `.__customPromise` will be true and `.___bluebirdPromise` will be false.
```js
var fs = require('fs')
var relike = require('relike')
var promise = relike(fs.readFile, 'package.json', 'utf8')
promise.then(JSON.parse).then(function (val) {
console.log(val.name) // => 'relike'
}, console.error)
console.log(promise.Promise) // => used Promise constructor
console.log(promise.___bluebirdPromise) // => `true` on old env, falsey otherwise
console.log(promise.___customPromise) // => `true` when pass `.Promise`, falsey otherwise
```
Or finally, you can pass Promise constructor as second argument to `.promisify` method. Like that
```js
const fs = require('fs')
const relike = require('relike')
const readFile = relike.promisify(fs.readFile, require('when'))
const promise = readFile('index.js')
console.log(promise.Promise) // => The `when` promise constructor, on old enviroments
console.log(promise.___customPromise) // => `true` on old environments
```
{% if (verb.related && verb.related.list && verb.related.list.length) { %}
## Related
{%= related(verb.related.list, {words: 12}) %}
{% } %}
## Contributing
Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](https://github.com/{%= repository %}/issues/new).
But before doing anything, please read the [CONTRIBUTING.md](./CONTRIBUTING.md) guidelines.
## [Charlike Make Reagent](http://j.mp/1stW47C) [![new message to charlike][new-message-img]][new-message-url] [![freenode #charlike][freenode-img]][freenode-url]
[![{%= author.username %}.tk][author-www-img]][author-www-url] [![keybase {%= author.username %}][keybase-img]][keybase-url] [![{%= author.username %} npm][author-npm-img]][author-npm-url] [![{%= author.username %} twitter][author-twitter-img]][author-twitter-url] [![{%= author.username %} github][author-github-img]][author-github-url]
{%= reflinks(verb.reflinks) %}
[npmjs-url]: https://www.npmjs.com/package/{%= name %}
[npmjs-img]: https://img.shields.io/npm/v/{%= name %}.svg?label={%= name %}
[license-url]: https://github.com/{%= repository %}/blob/master/LICENSE
[license-img]: https://img.shields.io/npm/l/{%= name %}.svg
[downloads-url]: https://www.npmjs.com/package/{%= name %}
[downloads-img]: https://img.shields.io/npm/dm/{%= name %}.svg
[codeclimate-url]: https://codeclimate.com/github/{%= repository %}
[codeclimate-img]: https://img.shields.io/codeclimate/github/{%= repository %}.svg
[travis-url]: https://travis-ci.org/{%= repository %}
[travis-img]: https://img.shields.io/travis/{%= repository %}/master.svg
[coveralls-url]: https://coveralls.io/r/{%= repository %}
[coveralls-img]: https://img.shields.io/coveralls/{%= repository %}.svg
[david-url]: https://david-dm.org/{%= repository %}
[david-img]: https://img.shields.io/david/{%= repository %}.svg
[standard-url]: https://github.com/feross/standard
[standard-img]: https://img.shields.io/badge/code%20style-standard-brightgreen.svg
[author-www-url]: http://www.{%= author.username.toLowerCase() %}.tk
[author-www-img]: https://img.shields.io/badge/www-{%= author.username.toLowerCase() %}.tk-fe7d37.svg
[keybase-url]: https://keybase.io/{%= author.username.toLowerCase() %}
[keybase-img]: https://img.shields.io/badge/keybase-{%= author.username.toLowerCase() %}-8a7967.svg
[author-npm-url]: https://www.npmjs.com/~{%= author.username.toLowerCase() %}
[author-npm-img]: https://img.shields.io/badge/npm-~{%= author.username.toLowerCase() %}-cb3837.svg
[author-twitter-url]: https://twitter.com/{%= author.username %}
[author-twitter-img]: https://img.shields.io/badge/twitter-@{%= author.username %}-55acee.svg
[author-github-url]: https://github.com/{%= author.username %}
[author-github-img]: https://img.shields.io/badge/github-@{%= author.username %}-4183c4.svg
[freenode-url]: http://webchat.freenode.net/?channels=charlike
[freenode-img]: https://img.shields.io/badge/freenode-%23charlike-5654a4.svg
[new-message-url]: https://github.com/{%= author.username %}/ama
[new-message-img]: https://img.shields.io/badge/ask%20me-anything-green.svg