http XHR module

http.js

function http ( url, config ) {
	var xhr = new XMLHttpRequest(),
		promise = {
          success: function () {},
          error: function () {}
        };
        
    config = config || {};

	config.async = config.async || true;
	config.method = config.method || 'GET';
	config.data = config.data || '';
  
	url = url || '/';

	xhr.open(config.method, url, config.async);
	xhr.send(config.data);

	if ( config.async ) {
		xhr.onreadystatechange = function() { // (3)
		  	if (xhr.readyState != 4) return;

		  	if ( xhr.status !== 200 ) {
				promise.error({
					status: xhr.status,
					error: xhr.statusText
				});
                
			} else {
				promise.success({
					status: 200, 
					response: xhr.responseText
				});
			}
		}
	} else {
		if ( xhr.status !== 200 ) {
			promise.error({
				status: xhr.status,
				error: xhr.statusText
			});
		} else {
			promise.success({
				status: 200, 
				response: xhr.responseText
			});
		}
	}

	return {
		then: function ( success, error ) {
			promise.success = success;
            promise.error = error;
		}
	};
}


//public
module.exports = http;

main.js

var http = require('./http');

http('http://jsonplaceholder.typicode.com/posts/1', {}).then(function successHandler( response ) {
  console.log(response);
}, function errorHandler( response ) {
  console.error(response);
})