javascript xml request

var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
       // Typical action to be performed when the document is ready:
       document.getElementById("demo").innerHTML = xhttp.responseText;
    }
};
xhttp.open("GET", "filename", true);
xhttp.send();

function httpGetAsync(url, callback) {
  var xmlHttp = new XMLHttpRequest();
  xmlHttp.onreadystatechange = function() { 
    if (xmlHttp.readyState == 4 && xmlHttp.status == 200)
      callback(xmlHttp.responseText);
  }
  xmlHttp.open("GET", url, true); // true for asynchronous 
  xmlHttp.send(null);
}

var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {

    if (this.readyState == 4 && this.status == 200) {

       // Action to be performed when the 
 document is read;

    }
};

xhttp.open("GET", "filename", true);

xhttp.send(); 

var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {

    if (this.readyState == 4 && this.status == 200) {

        // Typical action to be performed when the document is ready:
       
 document.getElementById("demo").innerHTML = xhttp.responseText;

    }
};

xhttp.open("GET", "filename", true);

xhttp.send();