# then
make it painless to adapt between callbacks and promises

## usage

`then` is like a magic portal to warp between Promised land and the firey depths of Callback hell.


```js
var then = require('th')
var fs = require('fs')

fs.readFile('./tmp', then())
then(function (file) {
  console.log('file')
}, function (err) {
  console.log('errors!', err)
})

// although you may want to be using streaming file methods, anyhow

```

When we invoke `then()` the first time, it creates a callback to give to `fs.readFile`. When we call it the next time, it's like a Promises/A+ `then` method.

Importantly, there are times when we want to go back from a chain of promises to a callback:

```js
function (err, nextCb) {
  if (err) { return nextCb(err) }
  var promise = myPromise()
    .then(someStep)
    .then(oneMoreThing)

  then.callback(promise, nextCb)
}
```


## api

### `then : () => Promise | (resolved: Function, rejected: Function) => Promise`
See usage note above for behavior.

### `then.callback(Promise<T>, Callback<T>) => void`
Registers the `callback` as a handler for promise `resolve` and `reject` events.


## installation

    $ npm install th


## running the tests

From package root:

    $ npm install
    $ npm test


## contributors

- jden <jason@denizac.org>


## license
MIT. (c) MMXIII AgileMD http://agilemd.com