Javascript ajax snippet from Mozilla

httprequest.js

  	(function() { 

			document.getElementById...

			.onclick = function() { sendHTTPRequest(); };  

			var httpRequest;
			function sendHTTPRequest() {
				if (window.XMLHttpRequest) { // Mozilla, Safari, ...
				    httpRequest = new XMLHttpRequest();
				} else if (window.ActiveXObject) { // IE 8 and older
				    httpRequest = new ActiveXObject("Microsoft.XMLHTTP");
				}
				
			    if (!httpRequest) {
			      console.log("Can't do ajax");
			      return false;
			    }

			    httpRequest.onreadystatechange = alertContents;
			    httpRequest.open('GET', url);
			    httpRequest.send();
			}

		    function alertContents() {
				if (httpRequest.readyState === 4) {
			    	if (httpRequest.status === 200) {
              httpRequest.responseText
			        } else {
			        	console.log('There was a problem with the request.');
			        }
			    }
		  	}
		})();