[JS] Tránh mất nội dung khi post bài

<script language=Javascript type=text/javascript>
// Cross browser event handling for IE 5+, NS6+ and Gecko
function addEvent(elm, evType, fn, useCapture)
{
if (elm.addEventListener)
{
// Gecko
elm.addEventListener(evType, fn, useCapture);
return true;
}
else if (elm.attachEvent)
{
// Internet Explorer
var r = elm.attachEvent('on' + evType, fn);
return r;
}
else
{
// nutscrape?
elm['on' + evType] = fn;
}
}

// Add Listeners
function addListeners(e)
{
// Before unload listener
addEvent(window, 'beforeunload', exitAlert, false);
}

// Exit Alert
function exitAlert(e)
{
var msg = "You will lose information if it has not already been saved.";

// set event
if (!e) { e = window.event; }
if (e) { e.returnValue = msg; }

// return warning message
return msg;
}

// Initialise
addEvent(window, 'load', addListeners, false);
</script>