Showing confirm message only sometimes in window.onbeforeload event? - javascript

When there are unsaved changes in my app I want to make sure the user does not close the window/tab without seeing a confirmation dialog.
I wrote this:
var _beforeWindowUnload = function(event) {
if (documentHasUnsavedChanges()) {
// document is dirty
var message = "Unsaved changes will be lost";
event.returnValue = message;
return message;
} else {
// document is clean
event.returnValue = null;
return null;
}
}
window.addEventListener('beforeunload', _beforeWindowUnload, false);
The problem is when the document is clean I still see the dialog with "null" message. I have tried with true and false too but no luck.
I also tried not returning anything when document is clean but then when it is dirty it won't show a message. This is odd!
How can I optionally avoid the confirmation dialog while still having the event listener?
Note 1: MDN says the following but apparently is not true?:
When this event returns a non-void value, the user is prompted to confirm the page unload. In most browsers, the return value of the event is displayed in this dialog.
Note 2: This should work on relatively new browsers.

Related

How do I ask the user to confirm they want to leave the page?

I have a web site that contains several pages where the user can add and edit information. In order to provide a consistent UI, I have the following JavaScript function...
function setWindowBeforeUnload(changed) {
$(window).on("beforeunload", function() {
if (confirmLeave && changed && changed()) {
return "You haven't saved the information. If you leave this page, the information will be lost.";
}
});
}
confirmLeave is a global variable that specifies if we are to ask them for confirmation before navigating away (which we don't if we are navigating to another page after a successful save). changed is a function that checks if the entity has changed.
This is called from a details page (say the customer page) as follows...
$(document).ready(function() {
setWindowBeforeUnload(customerChanged);
});
function customerChanged() {
// Checks the data and returns true or false as appropriate
}
This all worked fine until recently, when a change in Chrome broke it.
I have searched for hours, and found loads of people suggesting code like this...
addEventListener('beforeunload', function(event) {
event.returnValue = 'You have unsaved changes.';
});
...which works fine as it is, except that it fires the warning whenever they leave the page, irrespective of whether or not the data has changed.
As soon as I try to add any logic (such as my checking code in the first sample), it doesn't work...
function setWindowBeforeUnload(changed) {
addEventListener('beforeunload', function(event) {
if (confirmLeave && changed && changed()) {
event.returnValue = 'You have unsaved changes.';
}
});
}
With this code, I can navigate away from the page without getting a warning.
Is there any way to reproduce my original behaviour now?
You can use logic in the handler, you just can't have a custom message any more.
See the code below. Use the "Run code snippet" to simulate navigation. Run the snippet, run it again no confirm. Toggle the button to "false" run the snippet and get a confirm.
var test = true;
function otherTest() {
return true;
}
addEventListener('beforeunload', function(event) {
if(!test || !otherTest()) {
event.returnValue = 'You have unsaved changes.';
}
});
document.getElementById('theButton').addEventListener('click', function(event) {
test = !test;
this.innerHTML = test.toString();
});
<p>Click the button to turn the confirm on and off</p>
<button id="theButton">true</button>

Javascript Alert when click close button

I have the following code, When I click on close (X) button it shows error stored in variable s. Before the script was working good but now its not showing alert when i click on close button. Did i do any mistake in coding or I need to add some .js file for this to work.
var internalLink = false;
function pageUnload() {
if (!internalLink && location.protocol != 'http:') {
internalLink = true;
var s = 'Alert Message';
if (navigator.userAgent.indexOf("Firefox") > -1) {
alert(s);
}
setTimeout("location.href= 'foo.com'", 100);
return s;
}
}
window.onbeforeunload = pageUnload;
Or Can you provide me some other code so that when user clicks on close button. Browser will show alert stored in variable s. Note: Only show alert when click close, Not then when redirects to other link or when submit the form. it should not show any alert when click internal links.
There is very little that browsers will allow the onbeforeunload to do. Heck, not all of them even support it. I'm pretty sure Opera doesn't.
What this event is meant for is to show a confirmation box asking if you want to leave or not. That's it. You can't call alert or confirm, redirect the user, make an (asynchronous) AJAX call, or do a whole lot else.
What you can do is return a string. That returned string will be shown on a browser-rendered alert asking if you want to leave or not. Note: Firefox won't actually display your string (see bug# 588292).
var internalLink = false;
function pageUnload() {
if (!internalLink && location.protocol != 'http:') {
internalLink = true;
var s = 'Alert Message';
// You cannot alert or set location.href here
// This will show your message in a confirm popup
return s;
}
}
window.onbeforeunload = pageUnload;
So, as you can see browsers are very picky about how they handle or even trigger onbeforeunload. Use it with caution.
There is no "official" way to know whether the user clicked "leave" or "stay". The de facto way is to use the unload event and a setTimeout, but it's very hacky.
var internalLink = false,
stayTimeout, stayClicked;
function pageUnload() {
if(stayClicked){
// Don't run this multiple times
return;
}
if (!internalLink && location.protocol != 'http:') {
internalLink = true;
// To mark that we've ran this event once
stayClicked = true;
// If the user opted to stay, this will be ran
setTimeout(stayOnPage, 1000);
var s = 'Alert Message';
// You cannot alert or set location.href here
// This will show your message in a confirm popup
return s;
}
}
function stayOnPage(){
// The user opted to stay, do something
location.href= 'foo.com';
// If you are not going to redirect, set stayClicked to false
// otherwise leave it alone
// stayClicked = false;
}
function leavePage(){
// The user has chosen to leave the page, clear the timeout
clearTimeout(stayTimeout);
}
window.onbeforeunload = pageUnload;
window.unload = leavePage;
A much better solution would be to assign events to the <a> tags, use your own confirm box, then do whatever.
var a = document.getElementsByTagName('a');
for(var b in a){
a[b].addEventListener('click', function(e){
var c = confirm('Do you want to follow this link?');
if(c){
// The user wants to leave, let them
return true;
}
else{
// Otherwise block the link, and do whatever
e.preventDefault();
location.href= 'foo.com';
}
});
}
You have several problems in your code
1) don't hand a string to setTimeout but a function
wrong:
setTimeout("location.href= 'foo.com'", 100);
correct:
setTimeout(function(){location.href= 'foo.com'}, 100);
2) as per HTML5 spec, alert calls are allowed to be ignored in the onbeforeunload event (which apparently FF is doing).
3) Redirection is not allowed in the unload event either.
You are only allowed to return a string which is then prompted to the user (ask if they really want to leave the page). The event is cancelable, but you cannot redirect inside the event itself.
https://developer.mozilla.org/en-US/docs/Web/API/window.onbeforeunload

onbeforeunload event cause issue in IE8

I am using jQuery in our application. We have some Javascript code which validates if you modified any data. If user enter some values and click on some other link or something else then pop up comes which say:
"Are you sure you want to navigate away from this page? ... Press OK to continue, or Cancel to stay on the current page."
Its working fine in IE7, IE9 and and Firefox and other browser. But in IE8 it generates alert box which says:
"Stop running this script. The script on this page is causing your web browser to run slowly If it continue to run , your computer might become unresponsive".
Following is my Javascript which cause problem.
$(document).ready(function()
{
// Flag to display warning.
// If needToConfirm = true warning message will be displayed.
needToConfirm = false;
window.onbeforeunload = askConfirm;
function askConfirm()
{
if (needToConfirm)
{
// Message to be displayed in Warning.
return "Your data will be lost.";
}
}
// Add all form elements in argument.
$("select,input,textarea").live('change',function ()
{
needToConfirm = true;
});
// Add all form elements in argument.
$("select,input,textarea").live('keypress',function ()
{
needToConfirm = true;
});
// Use "class = noWarning" for save or cancel button.
$(".noWarning").click(function ()
{
needToConfirm = false;
});
});
Is it problem of window.onbeforeunload = askConfirm; code some thing else.
EDIT
Found that following line cause problem in IE8
$("select,input,textarea").live('keypress',function ()
{
needToConfirm = true;
});
Is it any other alternative for this.

Prevent a webpage from navigating away using JavaScript

How to prevent a webpage from navigating away using JavaScript?
Using onunload allows you to display messages, but will not interrupt the navigation (because it is too late). However, using onbeforeunload will interrupt navigation:
window.onbeforeunload = function() {
return "";
}
Note: An empty string is returned because newer browsers provide a message such as "Any unsaved changes will be lost" that cannot be overridden.
In older browsers you could specify the message to display in the prompt:
window.onbeforeunload = function() {
return "Are you sure you want to navigate away?";
}
Unlike other methods presented here, this bit of code will not cause the browser to display a warning asking the user if he wants to leave; instead, it exploits the evented nature of the DOM to redirect back to the current page (and thus cancel navigation) before the browser has a chance to unload it from memory.
Since it works by short-circuiting navigation directly, it cannot be used to prevent the page from being closed; however, it can be used to disable frame-busting.
(function () {
var location = window.document.location;
var preventNavigation = function () {
var originalHashValue = location.hash;
window.setTimeout(function () {
location.hash = 'preventNavigation' + ~~ (9999 * Math.random());
location.hash = originalHashValue;
}, 0);
};
window.addEventListener('beforeunload', preventNavigation, false);
window.addEventListener('unload', preventNavigation, false);
})();
Disclaimer: You should never do this. If a page has frame-busting code on it, please respect the wishes of the author.
The equivalent in a more modern and browser compatible way, using modern addEventListener APIs.
window.addEventListener('beforeunload', (event) => {
// Cancel the event as stated by the standard.
event.preventDefault();
// Chrome requires returnValue to be set.
event.returnValue = '';
});
Source: https://developer.mozilla.org/en-US/docs/Web/Events/beforeunload
I ended up with this slightly different version:
var dirty = false;
window.onbeforeunload = function() {
return dirty ? "If you leave this page you will lose your unsaved changes." : null;
}
Elsewhere I set the dirty flag to true when the form gets dirtied (or I otherwise want to prevent navigating away). This allows me to easily control whether or not the user gets the Confirm Navigation prompt.
With the text in the selected answer you see redundant prompts:
In Ayman's example by returning false you prevent the browser window/tab from closing.
window.onunload = function () {
alert('You are trying to leave.');
return false;
}
The equivalent to the accepted answer in jQuery 1.11:
$(window).on("beforeunload", function () {
return "Please don't leave me!";
});
JSFiddle example
altCognito's answer used the unload event, which happens too late for JavaScript to abort the navigation.
That suggested error message may duplicate the error message the browser already displays. In chrome, the 2 similar error messages are displayed one after another in the same window.
In chrome, the text displayed after the custom message is: "Are you sure you want to leave this page?". In firefox, it does not display our custom error message at all (but still displays the dialog).
A more appropriate error message might be:
window.onbeforeunload = function() {
return "If you leave this page, you will lose any unsaved changes.";
}
Or stackoverflow style: "You have started writing or editing a post."
If you are catching a browser back/forward button and don't want to navigate away, you can use:
window.addEventListener('popstate', function() {
if (window.location.origin !== 'http://example.com') {
// Do something if not your domain
} else if (window.location.href === 'http://example.com/sign-in/step-1') {
window.history.go(2); // Skip the already-signed-in pages if the forward button was clicked
} else if (window.location.href === 'http://example.com/sign-in/step-2') {
window.history.go(-2); // Skip the already-signed-in pages if the back button was clicked
} else {
// Let it do its thing
}
});
Otherwise, you can use the beforeunload event, but the message may or may not work cross-browser, and requires returning something that forces a built-in prompt.
Use onunload.
For jQuery, I think this works like so:
$(window).unload(function() {
alert("Unloading");
return falseIfYouWantToButBeCareful();
});
If you need to toggle the state back to no notification on exit, use the following line:
window.onbeforeunload = null;

How can I override the OnBeforeUnload dialog and replace it with my own?

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;
});

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