songbird

Chain promises easily in node.js

Songbird

Easily mix asynchronous and synchronous programming styles in node.js.

Mix promises into all the objects in your code base.

Songbird is built upon the bluebird promise library (hence the name).

If you have any questions about what methods the promises expose, go here to view the bluebird API.

A project by Matt Blair at https://github.com/duereg/songbird.

Songbird requires node version 0.6.x or greater.

npm install songbird

Would you rather write this:

var updateUser = function(idattributescallback) {
  User.findOne(id, function (erruser) {
    if (err) return callback(err);
 
    user.set(attributes);
    user.save(function(errupdated) {
      if (err) return callback(err);
 
      console.log("Updated", updated);
      callback(null, updated);
    });
  });
});

Or this, which behaves identically:

 
  User.promise.findOne(id).then( (user) →
    user.set(attributes)
    user.promise.save()
  ).then (user) -> console.log("Updated"user)

Using standard node callback-style APIs without Songbird, we write (from the fs docs):

fs.readFile('/etc/passwd', function (errdata) {
  if (err) throw err;
  console.log(data);
});

Using Songbird, we write:

fs.promise.readFile('/etc/passwd').then(console.log);

Songbird makes it much easier to work with asynchronous methods in an interactive console, or REPL.

If you find yourself in an interactive session, you can require Songbird so that you can use promise.

> fs = require('fs');
> require('songbird');
> fs.promise.readFile('/etc/passwd', 'utf8').then (data) → data.get()
$ songbird
Starting Songbird node REPL...
> fs = require('fs');
> fs.promise.readFile('/etc/passwd', 'utf8').then(console.log)
##
# User Database
#
...

Or for a CoffeeScript REPL:

$ songbird -c [or --coffee]
Starting Songbird coffee REPL...
coffee> fs = require 'fs'
coffee> fs.promise.readFile('/etc/passwd', 'utf8').then console.log
##
# User Database
#
...

Songbird mixes promise into Function.prototype so you can use them directly as in:

readFile = require('fs').readFile;
readFile.promise('/etc/passwd').then(console.log);

Songbird adds promise to Object.prototype correctly so they are not enumerable.

These proxy methods also ignore all getters, even those that may return functions. If you need to call a getter with Songbird that returns an asynchronous function, you can do:

func = obj.getter
func.promise.call(obj, args)

Requiring the songbird library not only updates the Object and Function prototype, but also returns a Promise library in which you can carry out certain actions that aren't easily handled from the the promise property.

For example: you have a situation where you're dealing with multiple promises, but don't care what order they complete in.

Promise = require("songbird");
 
Promise.all([task1, task2, task3]).spread(function(result1result2result3){
 
});

Normally when using .then the code would be like:

Promise = require("songbird");
 
Promise.all([task1, task2, task3]).then(function(results){
    var result1 = results[0];
    var result2 = results[1];
    var result3 = results[2];
});

For more information about the underlying bluebird promise API, the API docs are here.

Some people don't like libraries that mix in to Object.prototype and Function.prototype. If that's how you feel, then Songbird is probably not for you.

git clone git://github.com/duereg/songbird.git
npm install
npm test

Songbird is written in coffeescript with source in src/ compiled to lib/.

Tests are written with mocha and chai in test/.

Run tests with npm test which will also compile the coffeescript to lib/.

Pull requests are welcome. Please provide tests for your changes and features. Thanks!

(The MIT License)

Copyright (c) 2014 Matt Blair

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.