promisify-node-callback v1.0.2

Promisify Node Callback

A small util to convert a callback-based async function into a promise-based async function.

var promisify = require('promisify-node-callback'),
	readFile = promisify( require('fs').readFile );

readFile('./package.json').then(function(contents){
	//	do something with contents...
});

Example

Supposing a callback-based function structured as such:

function getFromDb(id, callback) {
	// does something async, returns `data` when good, `err` when bad
	if(err) {
		return callback(err);
	}
	return callback(null, err);
}

Consumption of this would normally look like this:

getFromDb(4, function(err, data){
	// check for errors via `err` var
	// do something with `data` which would represent record #4
})

Promisifying turns it into a promise

var db = promisify(getFromDb);

db(4)
	.then(function(data){
		// do something with data
	})
	.catch(function(err){
		// handle errors via err
	});

Gotchas

• It always expects the last paramater of an ansync function to be the callback.
• It expects the callback to look like: function(err, data), so async functions with 3-parameter callbacks need to be abstracted into 2 params.

Changelog

1.0.2

Fixed docs :(

1.0.1

Added documentation :/