XMLHttpRequest (XHR) is a JavaScript object that exposes an API for making asynchronous HTTP requests from frontend code running a Web browser — that is, for enabling the programming technique known as AJAX. The XHR API is a legacy API. It has been superseded by the Fetch API.
Example usage
function reqListener () {
console.log(this.responseText);
}
var oReq = new XMLHttpRequest();
oReq.addEventListener("load", reqListener);
oReq.open("GET", "http://www.example.org/example.txt");
oReq.send();
Taken from mozilla.org.
