Post request with JS without jQuery

sendPost = function(url, data) {
    var xmlhttp = new XMLHttpRequest();
    var params = serialize(data);

    xmlhttp.open("POST", url, true);
    xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
    xmlhttp.setRequestHeader("Content-length", params.length);
    xmlhttp.setRequestHeader("Connection", "close");

    xmlhttp.send(params);

    xmlhttp.onreadystatechange = function() {
        if (xmlhttp.readyState === 4 && xmlhttp.status === 200){
            console.log(xmlhttp.responseText);
        }
    };
}

serialize = function(obj, prefix) {
    var str = [];
    for(var p in obj) {
        var k = prefix ? prefix + "[" + p + "]" : p, v = obj[p];
        str.push(typeof v == "object" ?
                serialize(v, k) :
                encodeURIComponent(k) + "=" + encodeURIComponent(v));
    }
    return str.join("&");
}

sendPost("http://some/host", {login: 'me@abc.def', password: 'mypassword'});

curl 'http://some/host' --data 'login=me%40abc.def&password=mypassword'