kychervasya

var form = document.getElementById('testForm');
form.onsubmit = function (e) {
  e.preventDefault();

  var data = {};
  for (var i = 0, ii = form.length; i < ii; ++i) {
    var input = form[i];
    if (input.name) {
      data[input.name] = input.value;
    }
  }

  var xhr = new XMLHttpRequest();
  xhr.open('POST', 'url', true);
  xhr.setRequestHeader('Content-Type', 'application/json; charset=UTF-8');
      xhr.onreadystatechange = function() {
        if (xhr.readyState != 4) return;
        if (xhr.status != 200) {
           alert(xhr.status + ': ' + xhr.statusText);
        } else {
           console.log(xhr.response);
           alert(xhr.responseText);
        }
      }

  xhr.send(JSON.stringify(data));
}