<script language="JavaScript">
window.onbeforeunload = confirmExit;
function confirmExit()
{
return "You have attempted to leave this page. If you have made any changes to the fields without clicking the Save button, your changes will be lost. Are you sure you want to exit this page?";
}
</script>
window.onbeforeunload = function (e) {
var message = "Your confirmation message goes here.",
e = e || window.event;
// For IE and Firefox
if (e) {
e.returnValue = message;
}
// For Safari
return message;
};
Instead of an annoying confirmation popup, it would be nice to delay leaving just a bit (matter of milliseconds) to manage successfully posting the unsaved data to the server, which I managed for my site using writing dummy text to the console like this:
window.onbeforeunload=function(e){
// only take action (iterate) if my SCHEDULED_REQUEST object contains data
for (var key in SCHEDULED_REQUEST){
postRequest(SCHEDULED_REQUEST); // post and empty SCHEDULED_REQUEST object
for (var i=0;i<1000;i++){
// do something unnoticable but time consuming like writing a lot to console
console.log('buying some time to finish saving data');
};
break;
};
}; // no return string --> user will leave as normal but data is send to server
<cfset unloadCheck=0>//a ColdFusion precheck in my page generation to see if unload check is needed
var erMsg="";
$(document).ready(function(){
<cfif q.myData eq "">
<cfset unloadCheck=1>
$("#myInput").change(function(){
verify(); //function elsewhere that checks all fields and populates erMsg with error messages for any fail(s)
if(erMsg=="") window.onbeforeunload = null; //all OK so let them pass
else window.onbeforeunload = confirmExit(); //borrowed from Jantimon above;
});
});
<cfif unloadCheck><!--- if any are outstanding, set the error message and the unload alert --->
verify();
window.onbeforeunload = confirmExit;
function confirmExit() {return "Data is incomplete for this Case:"+erMsg;}
</cfif>