ajax without jQuery

ajax.js

var ajax = (function (ajax, json) {
	ajax.send = function (obj) {
		var xmlhttp = new XMLHttpRequest();

		xmlhttp.onreadystatechange = function () {
			if (xmlhttp.readyState == 4) {
				if (xmlhttp.status >= 200 && xmlhttp.status < 300 && obj.complete) {
					obj.complete(json.parse(xmlhttp.responseText));
				}
				if (xmlhttp.status < 200 || xmlhttp.status >= 300) {
					if (obj.error) obj.error(xmlhttp.response);
				}
			}
		}

		xmlhttp.open(obj.method, obj.url, true);
		xmlhttp.setRequestHeader('Content-type', 'application/json');
		xmlhttp.send(obj.data);
	};
	return ajax;
})(ajax || {}, JSON);

example.js

ajax.send({
	url: 'http://myDomain.com/resource',
	data: {
		field: 'value'
	},
	method: 'POST',
	complete: function(data) {
		//do something with data
	},
	error: function(data) {
		//handle error
	}
});