functions.js

function showMessage(msg, closeAfter){
    document.getElementById("error").innerHTML = msg;
    if(closeAfter !== undefined){
        setTimeout(function(){
            document.getElementById("error").innerHTML = "";
        },closeAfter);
    }
}

function getResponse(adr, callback, timeoutCallback, timeout, method){
    if(timeoutCallback === undefined) {
        timeoutCallback = function(){
            showMessage("error loading "+adr);
        };
    }
    if(timeout === undefined) timeout = 8000;
    if(method === undefined) method = "GET";
    var xmlhttp = new XMLHttpRequest();
    xmlhttp.onreadystatechange = function() {
        if(xmlhttp.readyState == 4){
            if(xmlhttp.status == 200){
                showMessage("");
                callback(xmlhttp.responseText);
            }
            else timeoutCallback();
        }
    };
    xmlhttp.open(method, adr, true);
    xmlhttp.send();
    xmlhttp.timeout = timeout;
    xmlhttp.ontimeout = timeoutCallback;
}