XMLHttpRequest()

var xhr = new XMLHttpRequest();
 xhr.open("GET", "URL", true);
 xhr.onreadystatechange = function() {
   if (xhr.readyState == 4) {
    data = JSON.parse(xhr.responseText);
      alert(data);
   }
 }
 xhr.send();
||
 xhr.onreadystatechange = function() {
    if(xhr.readyState == 4 && xhr.status == 200) {
        alert(xhr.responseText);
    }
}