robojones/smart-promisify

# smart-promisify
A smart implementation of promisify using native promises

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## Install

```bash
npm i smart-promisify
```

## Features

With smart-promisify you can obviously wrap asynchronous functions so they return a promise.

__But why smart?__

The smart thing about this promisify module is, that you can use the wrapped function just like before. If you provide a __callback__, no promise will be returned. If you don't provide a callback, you will get your __promise__.

You can also change the this object of the wrapped function. If you use .apply, .call or .bind on the wrapper, the __this object will also be applied to the wrapped function__.

## Example - Promisify fs.mkdir


```javascript
const fs = require('fs')
const promisify = require('smart-promisify')

// create an async function so we can await stuff
async function example () {

  // wrap the fs.mkdir method
  let mkdir = promisify(fs.mkdir)

  // await the promise returned by the wrapper
  await mkdir('folder1')

  // you can still provide a callback.
  // the wrapper will return the return value of the fs.mkdir instead of a promise
  mkdir('folder2', console.log)

  // changing the this of the promisified function
  mkdir.call(fs, 'folder3')
  // fs.mkdir will now have fs as its this object

  // alternatively you can call the promisify function with a second argument.
  mkdir = promisify(fs.mkdir, fs)
  // the second argument will be used as this object for the wrapped function, if it isn't changed afterwards by with call, bind or apply
}

example().catch(console.error)
```