promise-resolver

Turn a promises resolver methods into a node style callback

Install

$ npm install --save promise-resolver

Usage

var promiseResolver = require('promise-resolver');

// creates a standard "defer" object, with added "cb" property.
var defer = promiseResolver.defer(passThroughCallback);   

// rejects promise and calls passThroughCallback with same args
defer.cb(new Error('...')); 

// resolves promise and calls passThroughCallback with same args
defer.cb(null, 'result'); 

return defer.promise;

• defer.cb will resolve/reject the promise and call passThroughCallback
• Ensures that passThroughCallback is only called once.
• If passThroughCallback is provided, it is assumed to handle any errors, and so unhandledRejection errors on the promise will be suppressed. This avoids potentially confusing console warnings if users are handling errors via a callback and ignoring the returned promise.
• defer.resolve and defer.reject behave as expected.

Alternate Usage

var promiseResolver = require('promise-resolver');

return new Promise(function (resolve, reject) {
  var cb = promiseResolver(resolve, reject, passThroughCallback);
  
  cb(new Error('...'));
  
  cb(null, 'result');
});

This behaves similar to the defer method, with the only exception being that unhandledRejection errors are not automatically suppressed when passThroughCallback is supplied.

API

promiseResolver(resolve, reject, passThrough)

All arguments should be functions, null, or undefined.

• resolve - promise resolve function
• reject - promise reject function
• passThrough - a "pass through" node style (error first) callback.

Returns a node style callback: cb(err, result...)

Calling the callback will resolve or reject the promise (depending on the err argument). If it exists, the passThrough callback will be called with the same arguments.

promiseResolver.defer(passThrough, Promise)

• passThrough - a "pass through" node style callback as described above
• Promise - an alternate Promise constructor (will use global.Promise or bluebird by default).

The return value is a standard defer object with an additional cb property that is a node style resolver callback.

var defer = promiseResolver(passThroughCallback);
var cb = defer.cb;
  
cb(new Error('...')); // rejects promise and calls passThroughCallback with same args
cb(null, 'result'); // resolves promise and calls passThroughCallback with same args

return defer.promise;

defer.resolve, and defer.reject are also available on the defer object.

License

MIT © James Talmage