request.js

    function request(url, method, data, callback) {

        function ready() {
            if (httpRequest.readyState === XMLHttpRequest.DONE) {
                if (httpRequest.status === 200) {
                    callback(httpRequest.responseText);
                }
            }
        }

        var httpRequest = new XMLHttpRequest();
        httpRequest.onreadystatechange = ready;
        httpRequest.open(method, url);

        if (method == "POST") {
            httpRequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
        }

        httpRequest.send(data);
    }