An abstraction of the general GET method using new Promises in JS

promise.js

// An abstraction of the general GET method using 
// new Promises in JS
var get = function (url) {
	// returns a promise object
	return new Promise(function (resolve, reject) {
		// the callback to the Promise constructor
		// gets two callbacks as parameters
		// the first is meant to be invoked for succes
		// and second one for failures
		var request = new XMLHTTPRequest();
		
		request.open('GET', url);

		request.onload = function () {
			if (request.status === 200) {
				// invoke the success callback with the response
				resolve(request.response);
			} else {
				// if HTTP status was anything other than success
				// invoke the failure callback
				reject(new Error(request.statusText));
			}
		}

		// Handle network error
		request.onerror = function () {
			reject(new Error("Network Error"));
		}

		request.send();
	});
};

// Here's is how you will use it

var resolve = function (response) {
	console.log("Request was successful", response);
};

var reject = function (error) {
	console.error("Request Failed", error);
}

get("../dummy_url.json").then(resolve, reject);


var getJOSN = function () {
	// parse the plain text response into JSON
	// the 'then' method of the promise returns a promise itself
	get(url).then(JSON.parse);
}