Get promises out of callback APIs

Here: Where we are now. API methods return undefined and accept a callback as the last arg having a signature of (err, result).

There: Where we want to be. API methods don't require callbacks as the last arg, and instead return promise objects.

This lib is a temporary, ugly, intermediate, minimal hack to get from here to there, until such time as the APIs available to us return promises and don't require callbacks. That's all.

Install

npm install ugly-adapter

Use

var adapt = require('ugly-adapter')
  , promise = adapt(fs.readFile, 'data.text', 'utf8')

API

Call a bare function, return a promise.

var adapt = require('ugly-adapter')
  , promise = adapt(someFunction, ...args)

Call a method on an object, return a promise

var adapt = require('ugly-adapter')
  , promise = adapt.method(object, methodName, ...args)

FAQ

1. Aren't promises slow? This lib will return Bluebird promises if you've added them to your project, otherwise native. Either way the API is the same. This lib does not however explicitly depend on Bluebird; it has to be reachable by name from your project, in which case it will be auto-detected.
2. Doesn't Lib X already do this? Yes, and lots of other stuff besides. This lib is very minimal. If you're already using Lib X, you should probably keep using it and ignore this. If, however, you're using a generator trampoline like co and all you want are yieldables, maybe this is the ticket.
3. Is es6 required? Sort of. Bluebird (see above) or a global Promise constructor (which is part of es6) is required. If neither are found this lib will bounce down the runway and burst into flames.
4. Wouldn't "pretty" be better? Node / io.js will natively support promises one day, at which point things can be pretty. When it comes time to refactor my own modules to support that, I don't want to have to unpush a magic button, and until then I'd prefer my code to be explicit about its hacks and workarounds.