Javascript AJAX

XHR requests let you POST a request to a REST API, and update the page from a HTML event when it replies.

var payload = { "foo": "bar" };
var json_payload = JSON.stringify(payload);

var XHR = new XMLHttpRequest();

XHR.open("POST", "/path/on/site");
XHR.addEventListener("error", function() {
  console.log("An error occurred");
});
XHR.addEventListener("load", function() {
  document.getElementById("results").innerHTML = this.responseText;
});
XHR.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
XHR.send(json_payload);