How to use ajax without jquery with pure javascript

Here is a snippet code for ajax request..


var ajax = {};
ajax.x = function() {
    if (typeof XMLHttpRequest !== 'undefined') {
        return new XMLHttpRequest();
    }
    var versions = [
        "MSXML2.XmlHttp.6.0",
        "MSXML2.XmlHttp.5.0", 
        "MSXML2.XmlHttp.4.0",
        "MSXML2.XmlHttp.3.0", 
        "MSXML2.XmlHttp.2.0",
        "Microsoft.XmlHttp"
    ];

    var xhr;
    for(var i = 0; i < versions.length; i++) {
        try {
            xhr = new ActiveXObject(versions[i]);
            break;
        } catch (e) {
        }
    }
    return xhr;
};

ajax.send = function(url, callback, method, data, sync) {
    var x = ajax.x();
    x.open(method, url, sync);
    x.onreadystatechange = function() {
        if (x.readyState == 4) {
            callback(x.responseText)
        }
    };
    if (method == 'POST') {
        x.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
    }
    x.send(data)
};

ajax.get = function(url, data, callback, sync) {
    var query = [];
    for (var key in data) {
        query.push(encodeURIComponent(key) + '=' + encodeURIComponent(data[key]));
    }
    ajax.send(url + (query.length ? '?' + query.join('&') : ''), callback, 'GET', null, sync)
};

ajax.post = function(url, data, callback, sync) {
    var query = [];
    for (var key in data) {
        query.push(encodeURIComponent(key) + '=' + encodeURIComponent(data[key]));
    }
    ajax.send(url, callback, 'POST', query.join('&'), sync)
};


call ajax function by below method

ajax.get('/test.php', {foo: 'bar'}, function() {});