I need to warn users about unsaved changes before they leave a page (a pretty common problem).
window.onbeforeunload = handler
This works but it raises a default dialog with an irritating standard message that wraps my own text. I need to either completely replace the standard message, so my text is clear, or (even better) replace the entire dialog with a modal dialog using jQuery.
So far I have failed and I haven't found anyone else who seems to have an answer. Is it even possible?
Javascript in my page:
<script type="text/javascript">
window.onbeforeunload = closeIt;
</script>
The closeIt() function:
function closeIt()
{
if (changes == "true" || files == "true")
{
return "Here you can append a custom message to the default dialog.";
}
}
Using jQuery and jqModal I have tried this kind of thing (using a custom confirm dialog):
$(window).beforeunload(function () {
confirm('new message: ' + this.href + ' !', this.href);
return false;
});
which also doesn't work - I cannot seem to bind to the beforeunload event.
You can't modify the default dialogue for onbeforeunload, so your best bet may be to work with it.
window.onbeforeunload = function() {
return 'You have unsaved changes!';
}
Here's a reference to this from Microsoft:
When a string is assigned to the returnValue property of window.event, a dialog box appears that gives users the option to stay on the current page and retain the string that was assigned to it. The default statement that appears in the dialog box, "Are you sure you want to navigate away from this page? ... Press OK to continue, or Cancel to stay on the current page.", cannot be removed or altered.
The problem seems to be:
When onbeforeunload is called, it will take the return value of the handler as window.event.returnValue.
It will then parse the return value as a string (unless it is null).
Since false is parsed as a string, the dialogue box will fire, which will then pass an appropriate true/false.
The result is, there doesn't seem to be a way of assigning false to onbeforeunload to prevent it from the default dialogue.
Additional notes on jQuery:
Setting the event in jQuery may be problematic, as that allows other onbeforeunload events to occur as well. If you wish only for your unload event to occur I'd stick to plain ol' JavaScript for it.
jQuery doesn't have a shortcut for onbeforeunload so you'd have to use the generic bind syntax.
$(window).bind('beforeunload', function() {} );
Edit 09/04/2018: custom messages in onbeforeunload dialogs are deprecated since chrome-51 (cf: release note)
What worked for me, using jQuery and tested in IE8, Chrome and Firefox, is:
$(window).bind("beforeunload",function(event) {
if(hasChanged) return "You have unsaved changes";
});
It is important not to return anything if no prompt is required as there are differences between IE and other browser behaviours here.
While there isn't anything you can do about the box in some circumstances, you can intercept someone clicking on a link. For me, this was worth the effort for most scenarios and as a fallback, I've left the unload event.
I've used Boxy instead of the standard jQuery Dialog, it is available here: http://onehackoranother.com/projects/jquery/boxy/
$(':input').change(function() {
if(!is_dirty){
// When the user changes a field on this page, set our is_dirty flag.
is_dirty = true;
}
});
$('a').mousedown(function(e) {
if(is_dirty) {
// if the user navigates away from this page via an anchor link,
// popup a new boxy confirmation.
answer = Boxy.confirm("You have made some changes which you might want to save.");
}
});
window.onbeforeunload = function() {
if((is_dirty)&&(!answer)){
// call this if the box wasn't shown.
return 'You have made some changes which you might want to save.';
}
};
You could attach to another event, and filter more on what kind of anchor was clicked, but this works for me and what I want to do and serves as an example for others to use or improve. Thought I would share this for those wanting this solution.
I have cut out code, so this may not work as is.
1) Use onbeforeunload, not onunload.
2) The important thing is to avoid executing a return statement. I don't mean, by this, to avoid returning from your handler. You return all right, but you do it by ensuring that you reach the end of the function and DO NOT execute a return statement. Under these conditions the built-in standard dialog does not occur.
3) You can, if you use onbeforeunload, run an ajax call in your unbeforeunload handler to tidy up on the server, but it must be a synchronous one, and you have to wait for and handle the reply in your onbeforeunload handler (still respecting condition (2) above). I do this and it works fine. If you do a synchronous ajax call, everything is held up until the response comes back. If you do an asynchronous one, thinking that you don't care about the reply from the server, the page unload continues and your ajax call is aborted by this process - including a remote script if it's running.
This can't be done in chrome now to avoid spamming, refer to javascript onbeforeunload not showing custom message for more details.
Angular 9 approach:
constructor() {
window.addEventListener('beforeunload', (event: BeforeUnloadEvent) => {
if (this.generatedBarcodeIndex) {
event.preventDefault(); // for Firefox
event.returnValue = ''; // for Chrome
return '';
}
return false;
});
}
Browsers support and the removal of the custom message:
Chrome removed support for the custom message in ver 51 min
Opera removed support for the custom message in ver 38 min
Firefox removed support for the custom message in ver 44.0 min
Safari removed support for the custom message in ver 9.1 min
Try placing a return; instead of a message.. this is working most browsers for me.
(This only really prevents dialog's presents)
window.onbeforeunload = function(evt) {
//Your Extra Code
return;
}
You can detect which button (ok or cancel) pressed by user, because the onunload function called only when the user choise leaveing the page. Althoug in this funcion the possibilities is limited, because the DOM is being collapsed. You can run javascript, but the ajax POST doesn't do anything therefore you can't use this methode for automatic logout. But there is a solution for that. The window.open('logout.php') executed in the onunload funcion, so the user will logged out with a new window opening.
function onunload = (){
window.open('logout.php');
}
This code called when user leave the page or close the active window and user logged out by 'logout.php'.
The new window close immediately when logout php consist of code:
window.close();
I faced the same problem, I was ok to get its own dialog box with my message, but the problem I faced was :
1) It was giving message on all navigations I want it only for close click.
2) with my own confirmation message if user selects cancel it still shows the browser's default dialog box.
Following is the solutions code I found, which I wrote on my Master page.
function closeMe(evt) {
if (typeof evt == 'undefined') {
evt = window.event; }
if (evt && evt.clientX >= (window.event.screenX - 150) &&
evt.clientY >= -150 && evt.clientY <= 0) {
return "Do you want to log out of your current session?";
}
}
window.onbeforeunload = closeMe;
<script type="text/javascript">
window.onbeforeunload = function(evt) {
var message = 'Are you sure you want to leave?';
if (typeof evt == 'undefined') {
evt = window.event;
}
if (evt) {
evt.returnValue = message;
}
return message;
}
</script>
refer from http://www.codeprojectdownload.com
What about to use the specialized version of the "bind" command "one". Once the event handler executes the first time, it’s automatically removed as an event handler.
$(window).one("beforeunload", BeforeUnload);
Try this
$(window).bind('beforeunload', function (event) {
setTimeout(function () {
var retVal = confirm("Do you want to continue ?");
if (retVal == true) {
alert("User wants to continue!");
return true;
}
else {
window.stop();
return false;
}
});
return;
});
I want to open a popup when the user closes the last tab of the current site. The problems I have is that
when the browser prompts the user (onbeforeunload returning a non null value), then the popup is blocked by the browser (see case 1 below)
when the browser does not prompt anything to the user (onbeforeunload not returning anything), then the popup is not opened at all and seemed to be totally ignored by the browser (why is that?) (see case 2 below)
Case 1: prompt and popup blocked (code from this answer)
window.onbeforeunload = function (e) {
e = e || window.event;
window.open('http://localhost', '_blank');
// For IE and Firefox prior to version 4
if (e) {
e.returnValue = 'Sure?';
}
// For Safari
return 'Sure?';
};
Case 2: no prompt, no popup, page closing "normally"
window.onbeforeunload = function (e) {
e = e || window.event;
window.open('http://localhost', '_blank');
};
From the specification:
An algorithm is allowed to show a popup if any of the following conditions is true
The task in which the algorithm is running is currently processing an activation behavior whose click event was trusted.
The window closing is not a click event.
The task in which the algorithm is running is currently running the event listener for a trusted event whose type is in the following list:
unload is not in that list.
The task in which the algorithm is running was queued by an algorithm that was allowed to show a popup, and the chain of such algorithms started within a user-agent defined timeframe.
For example, if a user clicked a button, it might be acceptable for a popup to result from that after 4 seconds, but it would likely not be acceptable for a popup to result from that after 4 hours.
Again, no. The task wasn't queued.
It is not possible to open a popup in response to a user trying to leave your site. It would enable too many harmful behaviours (click on this advert, quit, popup, you must click on this advert, loop).
Here's my code:
var popWindow = true;
window.onbeforeunload = function() {
if(popWindow == true) {
popWindow = false;
return "Sure?";
}
}
http://jsfiddle.net/anam/su8dznoa/
I want to prompt user to either logout or stay on page as logged-in. I tried using the following code, but not able to find the correct solution:
window.onbeforeunload = function (e) {
var e = e || window.event;
// For IE and Firefox
if (e) {
e.returnValue = 'Any string';
}
alert(doLogout());
// For Safari
return 'Any string';
};
function doLogout(){
var r=confirm("Press a button!");
alert("confirmResponse: " + r);
return r;
}
When i tried closing the tab/window, it just asks for "This page is asking you to confirm that you want to leave - data you have entered may not be saved". In my code first confirm dialog should be popped up, which is not happening.
Any solutions ?
It won't do alert() because of security reasons. This tactic to prevent user from leaving the page was used too often by "bad guys of the internet" so most browser blocked it. Only thing you can do in onunload or onbeforeunload is pass a string that should be displayed to user, before he makes a decision to stay or leave page. You should put you message in place of 'Any string'. That should be sufficient for the user.
I need a JavaScript script that would disable users from closing using ALT+F4. I have looked everywhere but it just everyone just says it isn't advised.
May not even be possible, if it isn't I will just have to detect when the user does quit out this way and log it in a database.
Here is my current script, it detects if the user presses either ALT or F4, but I can't get it to cancel that key press. Is there a way to make the browser think the user pressed another key as well so the combo would be ALT + G + F4 for example, which would disrupt the ALT+F4 combo?
//Run on keydown, disable user from quiting via ALT+F4
document.onkeydown = function(evt) {
evt = evt || window.event;
//Get key unicode
var unicode = evt.keyCode ? evt.keyCode : evt.charCode;
//Check it it's ALT or F4 (115)
if (unicode == 115 || evt.altKey == 1)
{
window.event.cancelBubble = true;
window.event.returnValue = false;
}
};
That key event is (on most OSs I guess) processed by the OS before it'S even sent to the browser, so cancelling the event inside the browser won't help a thing - even if it was Javascript that is executed inside the browser's UI, not only the current document.
Therefore - what you're trying to do cannot be done.
One can prevent the resulting window closure with:
window.onbeforeunload = funcRef
I think readers landing here might want to be reminded of this (as I did).
For related details, see
Jquery prevent window closing
try to use the code below:
window.webContents.on("before-input-event",(event,input)=>{
if(input.code=='F4'&&input.alt)event.preventDefault();});
I want to detect and block certain keyboard shortcuts on a web page. For example, say I want to prevent alt+tab for switching apps (just an example, assume any global shortcut).
Here's as far as I can think it out:
attach a keyboard event listener to
document (or window?)
use event.which to check which key
combination was pressed
if it was a blacklisted shortcut,
stop the browser from executing it
But, I don't know how to
A) detect multiple keys (e.g. alt and tab together), or
B) stop them from executing (can I just return false?).
Can anyone tell me how to accomplish the above?
You want to prevent screenshots from being taken? Forget it right now.
No matter what elaborate mechanisms you put into place, they will be trivial to circumvent by un-focusing the browser window (or just the document, e.g. by clicking into the address bar), and pressing the screenshot key then.
There is no chance for you to do this except by installing client software on the computer that controls what the user does, or maybe using some proprietary ActiveX control that makes its contents un-print-screenable. Both approaches are hugely difficult and have tons of downsides.
You cannot block keyboard combinations that belong to the OS. Only keyboard combinations that roam inside the browser and are not OS specific.
If you want to protect your content, don't publish it in public. Or put a decent license on it
// lookup table for keycodes
var key = { s: 83 };
document.onkeydown = function (e) {
// normalize event
e = e || window.event;
// detecting multiple keys, e.g: Ctrl + S
if (e.ctrlKey && !e.altKey && e.keyCode === key.s) {
// prevent default action
if (e.preventDefault) {
e.preventDefault();
}
// IE
e.returnValue = false;
}
};
Detecting Keystrokes Compatibility Table (QuirksMode)