Promises

promises-mixing.js

var fn = function() { 
	var dfd = new Deferred(); 

	var promises = [];
	promises.push(async1()); // an async operation
	promises.push(async2()); // an async operation
	promises.push(sync1());  // a sync operation
	promises.push(async3()); // an async operation
	
        // You want to perform some computation after above 4 tasks are done.
	Promise.when(promises).done(function() { 
		for (var i = 0, len = arguments.length; i < len; i++) { 
			if (!arguments[i]) {
				dfd.resolve(false); 
			}
		}
		dfd.resolve(true); 
	}).fail(function(err) { 
		dfd.reject(err); 
	});
	
	return dfd.promise(); 
};