Javascript promises demo

	/**
	* Check out following URL's
	* http://www.html5rocks.com/en/tutorials/es6/promises/
	* http://www.html5rocks.com/en/tutorials/es6/promises/#toc-async
	* http://blog.parse.com/2013/01/29/whats-so-great-about-javascript-promises/
	* https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise
	*
	* Try this code out on http://repl.it/
	*
	* At present, promises are not yet supported by all browsers and some javascript libraries
	* offer this functionality already.
	*
	* Q seems to be a popular implementation but it's performance seems not that good
	* https://github.com/kriskowal/q
	*
	* Bleubird seems like the most promising implementation in terms of performance
	* https://github.com/petkaantonov/bluebird
	*
	* I hope to find some time soon to prepare a demo with bluebird.
	***/
	function factorial(n) {
	return new Promise(function(resolve, reject) {
	if (n < 0) {
	reject(new Error("n has to be larger than 0!!"));
	} else {
	var result = 1;
	do {
	result *= n;
	n--;
	}
	while (n > 1);
	return resolve(result);
	}
	});
	}
	function onSucces(result) {
	console.log("succesfully calculated " + result);
	}
	function onError(error) {
	console.log(error.toString());
	}
	factorial(5).then(onSucces, onError);
	//succesfully calculated 120
	factorial(-3).then(onSucces, onError);
	//Error: n has to be larger than 0!!

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