$.getJSON('/my/url', function(data) {
  console.log(data);
});

request = new XMLHttpRequest();
request.open('GET', '/my/url', true);

request.onload = function() {
  if (request.status >= 200 && request.status < 400){
    // Success!
    data = JSON.parse(request.responseText);
    console.log(data);
  } else {
    // We reached our target server, but it returned an error

  }
};

request.onerror = function() {
  // There was a connection error of some sort
};

request.send();