q-it-up v0.1.8

Q it Up

Magically* make functions which take callbacks instead return promises as provided by the magnificent Q library!

* not magically

qItUp = require('q-it-up');
request = qItUp(require('request'));

request('http://tfwiki.net').then(function(response) {
  return 'Got a ' + response.statusCode;
});

Installation

npm install q-it-up --save

Usage

Q-it-up provides a function which takes a CPS (continuation passing style) function and fills in the callback with one which resolves (or rejects) using a Q promise.

That is, any function which works by taking a callback with a signature where an error is passed as the first argument and results passed as the remaining arguments:

mult = function(a, b, callback) {
  return callback(null, a * b);
};

mult(7, 6, function(err, res) {
  return console.log(res);
});

This can be "Q'd up" to instead return a promise:

mult = qItUp(function(a, b, callback) {
  return callback(null, a * b); 
});

mult(7,6).then(console.log); // 42

If an error is passed to the callback, this will be rejected with Q:

fail = qItUp(function(message, callback) {
  return callback(message);
});

fail("An error occurred!").then(null, console.warn); // An error occurred!

If multiple values are passed to the callback on success these will be resolved as an array:

split = qItUp(function(str, separator, callback)) {
  return callback.apply(this, [ null ].concat(str.split(separator)));
  });

split('1:2:3', ':').then(function(results) {
   return console.log(results);
}); // [ 1, 2, 3 ]

A method on an object may be q'd up by specifying the object and the name of the method:

client = new ApiClient();

get = qItUp(client, 'get');

This ensures that the method is executed in the correct scope (that of the owning object).

TODO

Widen support to other patterns of CPS - separate error and success callbacks, callbacks where error and success parameters are at different positions, callbacks just for success.