simple typescript xhr using promises

XHR.ts

module XHR {

	export class Header {
		header: string;
		data: string;
		constructor(header: string, data: string) {
			this.header = header;
			this.data = data;
		}
	}

	export class Data {
		Headers: string;
		Body: string;
		Text: string;
		Type: string;
		Status: number;
		StatusText: string;
	}

	function DataFromJSXHR(jsXHR: XMLHttpRequest): Data {
		var data = new Data();
		data.Headers = jsXHR.getAllResponseHeaders();
		data.Body = jsXHR.responseBody;
		data.Text = jsXHR.responseText;
		data.Type = jsXHR.responseType;
		data.Status = jsXHR.status;
		data.StatusText = jsXHR.statusText;
		return data;
	}

	function SendCommand(
		method: string,
		url: string,
		headers: Array<Header>,
		data: string = ""): Q.Promise<Data> {

		var defer = Q.defer<Data>();

		var jsXHR = new XMLHttpRequest();
		jsXHR.open(method, url);

		if (headers != null)
			headers.forEach(header=>
				jsXHR.setRequestHeader(header.header, header.data));

		jsXHR.onload = (ev) => {
			if (jsXHR.status < 200 || jsXHR.status >= 300) {
				defer.reject(DataFromJSXHR(jsXHR));
			}
			defer.resolve(DataFromJSXHR(jsXHR));
		}
		jsXHR.onerror = (ev) => {
			defer.reject('Error ' + method.toUpperCase() + 'ing data to url "' + url + '", check that it exists and is accessible');
		};

		if (method == 'POST')
			jsXHR.send(data);
		else
			jsXHR.send();
		return defer.promise;
	}
	export function Get(
		url: string,
		headers: Array<Header> = null): Q.Promise<Data> {

		return SendCommand('GET', url, headers);
	}

	export function Post(
		url: string,
		data:string="",
		headers: Array<Header> = null): Q.Promise<Data> {

		return SendCommand('POST', url, headers, data);
	}
}