Converting Callback style code to promises

cb -> promise

var q = require('q');

// Sample Async Function
function asyncFunction(data, cb) {
	setTimeout(function() {
		// call cb with error
		cb(new Error('Error'));
		// Or call with success
		cb(null, {status: 'true'});
	}, 100);
}

// Converting Async fn to promises
// Q has an inbuilt function that does this called q.nfcall
// so the following function is the equivalent of :
// var promiseFunction = q.nfcall(asyncFunction, data);

function promiseFunction(data) {
	
	var d = q.defer();
	
	asyncFunction(data, function(err, res) {
		if(err) d.reject(err);
		else d.resolve(res);
	});
		
	return d.promise;
}

// Now you can call the promise function
promiseFunction('hello world')
.then(function(data) {
	// Do some more stuff
	return status;
})
.then(function(data) {
	// do more stuff
})
// the following catch will catch all errors in any .then step before it.
.catch(function(err) {
	// Handle the error here.
});