XMLHttpRequest not working in Mozilla

function addItem(str) {
	var request;
	if (window.XMLHttpRequest){//firefox etc.
		request = new XMLHttpRequest();
	}
	else if (window.ActiveXObject){//ie
		request = new ActiveXObject("Microsoft.XMLHTTP");
	}
	request.open('GET', "checkinout-actions/add-more-items-code.php?q="+str);
 
	request.onreadystatechange = function () {
		if (request.readyState == 1) { return }
		else if (request.readyState == 4) {
			if (request.status < 400) {
				// do your stuff here
				document.getElementById("txtHint").innerHTML=request.responseText;
			}
			else if (error != null)
				error(request);
		}
	};
	request.send();
	window.location.reload();
}