ajax.js

var Request = {
    method: "POST", 

    send: function(url, data, callback){
        var dataToSend = this.QueryString(data);
        var ajax = new XMLHttpRequest();

        ajax.open(this.method, url, true);
        ajax.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
        ajax.onreadystatechange = function(){
            if(ajax.readyState == 4 && ajax.status == 200){
                return callback(ajax.responseText);
            }
        };
        ajax.send(dataToSend);
    }, 

    QueryString: function(params){
        var str = "";

        if(typeof params === "object" && params.constructor == Object){ // това да се оправи
            for(var value in params){
                str += value + "=" + encodeURIComponent(params[value]) + "&";
            }
        }

        if(str.length > 0){
            str = str.substring(0, str.length - 1);
        }

        return str;
    }
};

/*
How to use: 

    Request.send("ajax.php", {
        "name1": "value_1", 
        "name2": "value_2", 
        "name3": "value_3"
    }, 
    function(result){
        console.log(result);
    });
*/