How can I detect when the user cancels a file input using an html file input?
onChange lets me detect when they choose a file, but I would also like to know when they cancel (close the file choose dialog without selecting anything).
While not a direct solution, and also bad in that it only (as far as I've tested) works with onfocus (requiring a pretty limiting event blocking) you can achieve it with the following:
document.body.onfocus = function(){ /*rock it*/ }
What's nice about this, is that you can attach/detach it in time with the file event, and it also seems to work fine with hidden inputs (a definite perk if you're using a visual workaround for the crappy default input type='file'). After that, you just need to figure out if the input value changed.
An example:
var godzilla = document.getElementById('godzilla')
godzilla.onclick = charge
function charge()
{
document.body.onfocus = roar
console.log('chargin')
}
function roar()
{
if(godzilla.value.length) alert('ROAR! FILES!')
else alert('*empty wheeze*')
document.body.onfocus = null
console.log('depleted')
}
See it in action: http://jsfiddle.net/Shiboe/yuK3r/6/
Sadly, it only seems to work on webkit browsers. Maybe someone else can figure out the firefox/IE solution
So I'll throw my hat into this question since I came up with a novel solution. I have a Progressive Web App which allows users to capture photos and videos and upload them. We use WebRTC when possible, but fall back to HTML5 file pickers for devices with less support *cough Safari cough*. If you're working specifically on an Android/iOS mobile web application which uses the native camera to capture photos/videos directly, then this is the best solution I have come across.
The crux of this problem is that when the page loads, the file is null, but then when the user opens the dialog and presses "Cancel", the file is still null, hence it did not "change", so no "change" event is triggered. For desktops, this isn't too bad because most desktop UI's aren't dependent on knowing when a cancel is invoked, but mobile UI's which bring up the camera to capture a photo/video are very dependent on knowing when a cancel is pressed.
I originally used the document.body.onfocus event to detect when the user returned from the file picker, and this worked for most devices, but iOS 11.3 broke it as that event is not triggered.
Concept
My solution to this is *shudder* to measure CPU timing to determine if the page is currently in the foreground or the background. On mobile devices, processing time is given to the app currently in the foreground. When a camera is visible it will steal CPU time and deprioritize the browser. All we need to do is measure how much processing time our page is given, when camera launches our available time will drop drastically. When the camera is dismissed (either cancelled or otherwise), our available time spike back up.
Implementation
We can measure CPU timing by using setTimeout() to invoke a callback in X milliseconds, and then measure how long it took to actually invoke it. The browser will never invoke it exactly after X milliseconds, but if it is reasonable close then we must be in the foreground. If the browser is very far away (over 10x slower than requested) then we must be in the background. A basic implementation of this is like so:
function waitForCameraDismiss() {
const REQUESTED_DELAY_MS = 25;
const ALLOWED_MARGIN_OF_ERROR_MS = 25;
const MAX_REASONABLE_DELAY_MS =
REQUESTED_DELAY_MS + ALLOWED_MARGIN_OF_ERROR_MS;
const MAX_TRIALS_TO_RECORD = 10;
const triggerDelays = [];
let lastTriggerTime = Date.now();
return new Promise((resolve) => {
const evtTimer = () => {
// Add the time since the last run
const now = Date.now();
triggerDelays.push(now - lastTriggerTime);
lastTriggerTime = now;
// Wait until we have enough trials before interpreting them.
if (triggerDelays.length < MAX_TRIALS_TO_RECORD) {
window.setTimeout(evtTimer, REQUESTED_DELAY_MS);
return;
}
// Only maintain the last few event delays as trials so as not
// to penalize a long time in the camera and to avoid exploding
// memory.
if (triggerDelays.length > MAX_TRIALS_TO_RECORD) {
triggerDelays.shift();
}
// Compute the average of all trials. If it is outside the
// acceptable margin of error, then the user must have the
// camera open. If it is within the margin of error, then the
// user must have dismissed the camera and returned to the page.
const averageDelay =
triggerDelays.reduce((l, r) => l + r) / triggerDelays.length
if (averageDelay < MAX_REASONABLE_DELAY_MS) {
// Beyond any reasonable doubt, the user has returned from the
// camera
resolve();
} else {
// Probably not returned from camera, run another trial.
window.setTimeout(evtTimer, REQUESTED_DELAY_MS);
}
};
window.setTimeout(evtTimer, REQUESTED_DELAY_MS);
});
}
I tested this on recent version of iOS and Android, bringing up the native camera by setting the attributes on the <input /> element.
<input type="file" accept="image/*" capture="camera" />
<input type="file" accept="video/*" capture="camcorder" />
This works out actually a lot better than I expected. It runs 10 trials by requesting a timer to be invoked in 25 milliseconds. It then measures how long it actually took to invoke, and if the average of 10 trials is less than 50 milliseconds, we assume that we must be in the foreground and the camera is gone. If it is greater than 50 milliseconds, then we must still be in the background and should continue to wait.
Some additional details
I used setTimeout() rather than setInterval() because the latter can queue multiple invocations which execute immediately after each other. This could drastically increase the noise in our data, so I stuck with setTimeout() even though it is a little more complicated to do so.
These particular numbers worked well for me, though I have see at least once instance where the camera dismiss was detected prematurely. I believe this is because the camera may be slow to open, and the device may run 10 trials before it actually becomes backgrounded. Adding more trials or waiting some 25-50 milliseconds before starting this function may be a workaround for that.
Desktop
Unfortuantely, this doesn't really work for desktop browsers. In theory the same trick is possible as they do prioritize the current page over backgrounded pages. However many desktops have enough resources to keep the page running at full speed even when backgrounded, so this strategy doesn't really work in practice.
Alternative solutions
One alternative solution not many people mention that I did explore was mocking a FileList. We start with null in the <input /> and then if the user opens the camera and cancels they come back to null, which is not a change and no event will trigger. One solution would be to assign a dummy file to the <input /> at page start, therefore setting to null would be a change which would trigger the appropriate event.
Unfortunately, there's no way official way to create a FileList, and the <input /> element requires a FileList in particular and will not accept any other value besides null. Naturally, FileList objects cannot be directly constructed, do to some old security issue which isn't even relevant anymore apparently. The only way to get ahold of one outside of an <input /> element is to utilize a hack which copy-pastes data to fake a clipboard event which can contain a FileList object (you're basically faking a drag-and-drop-a-file-on-your-website event). This is possible in Firefox, but not for iOS Safari, so it was not viable for my particular use case.
Browsers, please...
Needless to say this is patently ridiculous. The fact that web pages are given zero notification that a critical UI element has changed is simply laughable. This is really a bug in the spec, as it was never intended for a full-screen media capture UI, and not triggering the "change" event is technically to spec.
However, can browser vendors please recognize the reality of this? This could be solved with either a new "done" event which is triggered even when no change occurs, or you could just trigger "change" anyways. Yeah, that would be against spec, but it is trivial for me to dedup a change event on the JavaScript side, yet fundamentally impossible to invent my own "done" event. Even my solution is really just heuristics, if offer no guarantees on the state of the browser.
As it stands, this API is fundamentally unusable for mobile devices, and I think a relatively simple browser change could make this infinitely easier for web developers *steps off soap box*.
You can't.
The result of the file dialog is not exposed to the browser.
When you select a file and click open/cancel, the input element should lose focus aka blur. Assuming the initial value of the input is empty, any non empty value in your blur handler would indicate an OK, and an empty value would mean a Cancel.
UPDATE: The blur is not triggered when the input is hidden. So can't use this trick with IFRAME-based uploads, unless you want to temporarily display the input.
Most of these solutions don't work for me.
The problem is that you never know which event will be triggered fist,
is it click or is it change? You can't assume any order, because it probably depends on the browser's implementation.
At least in Opera and Chrome (late 2015) click is triggered just before 'filling' input with files, so you will never know the length of files.length != 0 until you delay click to be triggered after change.
Here is code:
var inputfile = $("#yourid");
inputfile.on("change click", function(ev){
if (ev.originalEvent != null){
console.log("OK clicked");
}
document.body.onfocus = function(){
document.body.onfocus = null;
setTimeout(function(){
if (inputfile.val().length === 0) console.log("Cancel clicked");
}, 1000);
};
});
/* Tested on Google Chrome */
$("input[type=file]").bind("change", function() {
var selected_file_name = $(this).val();
if ( selected_file_name.length > 0 ) {
/* Some file selected */
}
else {
/* No file selected or cancel/close
dialog button clicked */
/* If user has select a file before,
when they submit, it will treated as
no file selected */
}
});
The new File System Access API will make our life easy again :)
try {
const [fileHandle] = await window.showOpenFilePicker();
const file = await fileHandle.getFile();
// ...
}
catch (e) {
console.log('Cancelled, no file selected');
}
Browser support is very limited (Jan, 2021). The example code works well in Chrome Desktop 86.
Just listen to the click event as well.
Following from Shiboe's example, here's a jQuery example:
var godzilla = $('#godzilla');
var godzillaBtn = $('#godzilla-btn');
godzillaBtn.on('click', function(){
godzilla.trigger('click');
});
godzilla.on('change click', function(){
if (godzilla.val() != '') {
$('#state').html('You have chosen a Mech!');
} else {
$('#state').html('Choose your Mech!');
}
});
You can see it in action here: http://jsfiddle.net/T3Vwz
You can catch the cancel if you choose the same file as previously and you click cancel: in this case.
You can do it like this:
<input type="file" id="myinputfile"/>
<script>
document.getElementById('myinputfile').addEventListener('change', myMethod, false);
function myMethod(evt) {
var files = evt.target.files;
f= files[0];
if (f==undefined) {
// the user has clicked on cancel
}
else if (f.name.match(".*\.jpg")|| f.name.match(".*\.png")) {
//.... the user has choosen an image file
var reader = new FileReader();
reader.onload = function(evt) {
try {
myimage.src=evt.target.result;
...
} catch (err) {
...
}
};
}
reader.readAsDataURL(f);
</script>
The easiest way is to check if there are any files in temporary memory. If you want to get the change event every time user clicks the file input you can trigger it.
var yourFileInput = $("#yourFileInput");
yourFileInput.on('mouseup', function() {
$(this).trigger("change");
}).on('change', function() {
if (this.files.length) {
//User chose a picture
} else {
//User clicked cancel
}
});
In my case i had to hide submit button while users were selecting images.
This is what i come up:
$(document).on('click', '#image-field', function(e) {
$('.submit-button').prop('disabled', true)
})
$(document).on('focus', '#image-field'), function(e) {
$('.submit-button').prop('disabled', false)
})
#image-field is my file selector. When somenone clicks on it, i disable the form submit button. The point is, when the file dialog closed - doesn't matter they select a file or cancel - #image-field got the focus back, so i listen on that event.
UPDATE
I found that, this does not work in safari and poltergeist/phantomjs. Take this info into account if you would like to implement it.
Shiboe's solution would be a good one if it worked on mobile webkit, but it doesn't. What I can come up with is to add a mousemove event listener to some dom object at the time that the file input window is opened, like so:
$('.upload-progress').mousemove(function() {
checkForFiles(this);
});
checkForFiles = function(me) {
var filefield = $('#myfileinput');
var files = filefield.get(0).files;
if (files == undefined || files[0] == undefined) $(me).remove(); // user cancelled the upload
};
The mousemove event is blocked from the page while the file dialog is open, and when its closed one checks to see if there are any files in the file input. In my case I want an activity indicator blocking things till the file is uploaded, so I only want to remove my indicator on cancel.
However this doesn't solve for mobile, since there is no mouse to move. My solution there is less than perfect, but I think its good enough.
$('.upload-progress').bind('touchstart', function() {
checkForFiles(this);
});
Now we're listening for a touch on the screen to do the same files check. I'm pretty confident that the user's finger will be put on the screen pretty quickly after cancel and dismiss this activity indicator.
One could also just add the activity indicator on the file input change event, but on mobile there is often a few seconds lag between selecting the image and the change event firing, so its just much better UX for the activity indicator to be displayed at the start of the process.
I found this atribute, its most simple yet.
if ($('#selectedFile')[0].files.length > 1)
{
// Clicked on 'open' with file
} else {
// Clicked on 'cancel'
}
Here, selectedFile is an input type=file.
I know this is a very old question but just in case it helps someone, I found when using the onmousemove event to detect the cancel, that it was necessary to test for two or more such events in a short space of time.
This was because single onmousemove events are generated by the browser (Chrome 65) each time the cursor is moved out of the select file dialog window and each time it is moved out of the main window and back in.
A simple counter of mouse movement events coupled with a short duration timeout to reset the counter back to zero worked a treat.
Combining Shiboe's and alx's solutions, i've got the most reliable code:
var selector = $('<input/>')
.attr({ /* just for example, use your own attributes */
"id": "FilesSelector",
"name": "File",
"type": "file",
"contentEditable": "false" /* if you "click" on input via label, this prevents IE7-8 from just setting caret into file input's text filed*/
})
.on("click.filesSelector", function () {
/* do some magic here, e.g. invoke callback for selection begin */
var cancelled = false; /* need this because .one calls handler once for each event type */
setTimeout(function () {
$(document).one("mousemove.filesSelector focusin.filesSelector", function () {
/* namespace is optional */
if (selector.val().length === 0 && !cancelled) {
cancelled = true; /* prevent double cancel */
/* that's the point of cancel, */
}
});
}, 1); /* 1 is enough as we just need to delay until first available tick */
})
.on("change.filesSelector", function () {
/* do some magic here, e.g. invoke callback for successful selection */
})
.appendTo(yourHolder).end(); /* just for example */
Generally, mousemove event does the trick, but in case user made a click and than:
cancelled file open dialog by escape key (without moving a mouse), made another accurate click to open file dialog again...
switched focus to any other application, than came back to browser's file open dialog and closed it, than opened again via enter or space key...
... we won't get mousemove event hence no cancel callback. Moreover, if user cancels second dialog and makes a mouse move, we'll get 2 cancel callbacks.
Fortunately, special jQuery focusIn event bubbles up to the document in both cases, helping us to avoid such situations. The only limitation is if one blocks focusIn event either.
I see that my response would be quite outdated, but never the less.
I faced with the same problem. So here's my solution.
The most useful code snipped was KGA's one. But it isn't totally working and is a bit complicated. But I simplified it.
Also, the main trouble maker was that fact, that 'change' event doesn't come instantly after focus, so we have to wait for some time.
"#appendfile" - which user clicks on to append a new file.
Hrefs get focus events.
$("#appendfile").one("focusin", function () {
// no matter - user uploaded file or canceled,
// appendfile gets focus
// change doesn't come instantly after focus, so we have to wait for some time
// wrapper represents an element where a new file input is placed into
setTimeout(function(){
if (wrapper.find("input.fileinput").val() != "") {
// user has uploaded some file
// add your logic for new file here
}
else {
// user canceled file upload
// you have to remove a fileinput element from DOM
}
}, 900);
});
You can detect this only in limited circumstances. Specifically, in chrome if a file was selected earlier and then the file dialog is clicked and cancel clicked, Chrome clears the file and fires the onChange event.
https://code.google.com/p/chromium/issues/detail?id=2508
In this scenario, you can detect this by handling the onChange event and checking the files property.
This is hacky at best, but here is a working example of my solution to detect whether or not a user has uploaded a file, and only allowing them to proceed if they have uploaded a file.
Basically hide the Continue, Save, Proceed or whatever your button is. Then in the JavaScript you grab the file name. If the file name does not have a value, then do not show the Continue button. If it does have a value, then show the button. This also works if they at first upload a file and then they try to upload a different file and click cancel.
Here is the code.
HTML:
<div class="container">
<div class="row">
<input class="file-input" type="file" accept="image/*" name="fileUpload" id="fileUpload" capture="camera">
<label for="fileUpload" id="file-upload-btn">Capture or Upload Photo</label>
</div>
<div class="row padding-top-two-em">
<input class="btn btn-success hidden" id="accept-btn" type="submit" value="Accept & Continue"/>
<button class="btn btn-danger">Back</button>
</div></div>
JavaScript:
$('#fileUpload').change(function () {
var fileName = $('#fileUpload').val();
if (fileName != "") {
$('#file-upload-btn').html(fileName);
$('#accept-btn').removeClass('hidden').addClass('show');
} else {
$('#file-upload-btn').html("Upload File");
$('#accept-btn').addClass('hidden');
}
});
CSS:
.file-input {
width: 0.1px;
height: 0.1px;
opacity: 0;
overflow: hidden;
position: absolute;
z-index: -1;
}
.file-input + label {
font-size: 1.25em;
font-weight: normal;
color: white;
background-color: blue;
display: inline-block;
padding: 5px;
}
.file-input:focus + label,
.file-input + label:hover {
background-color: red;
}
.file-input + label {
cursor: pointer;
}
.file-input + label * {
pointer-events: none;
}
For the CSS a lot of this is to make the website and button accessible for everyone. Style your button to whatever you like.
The following seems to work for me (on desktop, windows):
var openFile = function (mimeType, fileExtension) {
var defer = $q.defer();
var uploadInput = document.createElement("input");
uploadInput.type = 'file';
uploadInput.accept = '.' + fileExtension + ',' + mimeType;
var hasActivated = false;
var hasChangedBeenCalled = false;
var hasFocusBeenCalled = false;
var focusCallback = function () {
if (hasActivated) {
hasFocusBeenCalled = true;
document.removeEventListener('focus', focusCallback, true);
setTimeout(function () {
if (!hasChangedBeenCalled) {
uploadInput.removeEventListener('change', changedCallback, true);
defer.resolve(null);
}
}, 300);
}
};
var changedCallback = function () {
uploadInput.removeEventListener('change', changedCallback, true);
if (!hasFocusBeenCalled) {
document.removeEventListener('focus', focusCallback, true);
}
hasChangedBeenCalled = true;
if (uploadInput.files.length === 1) {
//File picked
var reader = new FileReader();
reader.onload = function (e) {
defer.resolve(e.target.result);
};
reader.readAsText(uploadInput.files[0]);
}
else {
defer.resolve(null);
}
};
document.addEventListener('focus', focusCallback, true); //Detect cancel
uploadInput.addEventListener('change', changedCallback, true); //Detect when a file is picked
uploadInput.click();
hasActivated = true;
return defer.promise;
}
This does use angularjs $q but you should be able to replace it with any other promise framework if needed.
Tested on IE11, Edge, Chrome, Firefox, but it does not seem to work on Chrome on a Android Tablet as it does not fire the Focus event.
The file-type field, frustratingly, doesn't respond to a lot of events (blur would be lovely). I see a lot of people suggesting change-oriented solutions and them getting downvoted.
change does work, but it has a major flaw (vs what we want to happen).
When you freshly load a page containing a file field, open the box and press cancel. Nothing, frustratingly, changes.
What I chose to do is load in a gated-state.
The next part of the form a section#after-image in my case is hidden from view. When my file field changes, an upload button is shown. Upon successful upload, section#after-image is shown.
If the user loads, opens the file-dialog, then cancels out, they never see the upload button.
If the user chooses a file, the upload button is shown. If they then open the dialog and cancel, the change event is triggered by this cancel, and there I can (and do) re-hide my upload button until a proper file is selected.
I was fortunate that this gated-state was already the design of my form. You do not need to use the same style, merely having the upload button initially hidden and upon change, setting a hidden field or javascript variable to something you can monitor on submit.
I tried changing the value of files[0] before the field was interacted with. This didn't do anything regarding onchange.
So yes, change works, at least as good as we're going to get. The filefield is secured, for obvious reasons, but to the frustration of well-intentioned developers.
It's not fitting to my purpose, but you might be able to, onclick, load a warning prompt (not an alert(), because that stalls page-processing), and hide it if change is triggered and files[0] is null. If change is not triggered, the div remains in its state.
Solution for file selection with hidden input
Note: this code doesn't detect cancellation, it offers a way to circumvent the need to detect it in a common case in which people try to detect it.
I got here while looking for a solution for file uploads using a hidden input, I believe that this is the most common reason to look for a way to detect cancellation of file input (open file dialog -> if a file was selected then run some code, otherwise do nothing), here's my solution:
var fileSelectorResolve;
var fileSelector = document.createElement('input');
fileSelector.setAttribute('type', 'file');
fileSelector.addEventListener('input', function(){
fileSelectorResolve(this.files[0]);
fileSelectorResolve = null;
fileSelector.value = '';
});
function selectFile(){
if(fileSelectorResolve){
fileSelectorResolve();
fileSelectorResolve = null;
}
return new Promise(function(resolve){
fileSelectorResolve = resolve;
fileSelector.dispatchEvent(new MouseEvent('click'));
});
}
Usage example:
Note that if no file was selected then the first line will return only once selectFile() is called again (or if you called fileSelectorResolve() from elsewhere).
async function logFileName(){
const file = await selectFile();
if(!file) return;
console.log(file.name);
}
Another example:
async function uploadFile(){
const file = await selectFile();
if(!file) return;
// ... make an ajax call here to upload the file ...
}
There is a hackish way to do this (add callbacks or resolve some deferred/promise implementation instead of alert() calls):
var result = null;
$('<input type="file" />')
.on('change', function () {
result = this.files[0];
alert('selected!');
})
.click();
setTimeout(function () {
$(document).one('mousemove', function () {
if (!result) {
alert('cancelled');
}
});
}, 1000);
How it works: while file selection dialog is open, document does not receive mouse pointer events. There is 1000ms delay to allow the dialog to actually appear and block browser window. Checked in Chrome and Firefox (Windows only).
But this is not a reliable way to detect cancelled dialog, of course. Though, might improve some UI behavior for you.
Here is my solution, using the file input focus (not using any timers)
var fileInputSelectionInitiated = false;
function fileInputAnimationStart() {
fileInputSelectionInitiated = true;
if (!$("#image-selector-area-icon").hasClass("fa-spin"))
$("#image-selector-area-icon").addClass("fa-spin");
if (!$("#image-selector-button-icon").hasClass("fa-spin"))
$("#image-selector-button-icon").addClass("fa-spin");
}
function fileInputAnimationStop() {
fileInputSelectionInitiated = false;
if ($("#image-selector-area-icon").hasClass("fa-spin"))
$("#image-selector-area-icon").removeClass("fa-spin");
if ($("#image-selector-button-icon").hasClass("fa-spin"))
$("#image-selector-button-icon").removeClass("fa-spin");
}
$("#image-selector-area-wrapper").click(function (e) {
$("#fileinput").focus();
$("#fileinput").click();
});
$("#preview-image-wrapper").click(function (e) {
$("#fileinput").focus();
$("#fileinput").click();
});
$("#fileinput").click(function (e) {
fileInputAnimationStart();
});
$("#fileinput").focus(function (e) {
fileInputAnimationStop();
});
$("#fileinput").change(function(e) {
// ...
}
Well, this doesn't exactly answers your question. My assumption is that, you have a scenario, when you add a file input, and invoke file selection, and if user hits cancel, you just remove the input.
If this is the case, then: Why adding empty file input?
Create the one on the fly, but add it to DOM only when it is filled in. Like so:
var fileInput = $("<input type='file' name='files' style='display: none' />");
fileInput.bind("change", function() {
if (fileInput.val() !== null) {
// if has value add it to DOM
$("#files").append(fileInput);
}
}).click();
So here I create <input type="file" /> on the fly, bind to it's change event and then immediately invoke click. On change will fire only when user selects a file and hits Ok, otherwise input will not be added to DOM, therefore will not be submitted.
Working example here: https://jsfiddle.net/69g0Lxno/3/
//Use hover instead of blur
var fileInput = $("#fileInput");
if (fileInput.is(":hover") {
//open
} else {
}
function file_click() {
document.body.onfocus = () => {
setTimeout(_=>{
let file_input = document.getElementById('file_input');
if (!file_input.value) alert('please choose file ')
else alert(file_input.value)
document.body.onfocus = null
},100)
}
}
Using setTimeout to get the certain value of the input.
If you already require JQuery, this solution might do the work (this is the exact same code I actually needed in my case, although using a Promise is just to force the code to wait until file selection has been resolved):
await new Promise(resolve => {
const input = $("<input type='file'/>");
input.on('change', function() {
resolve($(this).val());
});
$('body').one('focus', '*', e => {
resolve(null);
e.stopPropagation();
});
input.click();
});
There are several proposed solutions in this thread and this difficulty to detecting when the user clicks the "Cancel" button on the file selection box is a problem that affects many people.
The fact is that there is no 100% reliable way to detect if the user has clicked the "Cancel" button on the file selection box. But there are ways to reliably detect if the user has added a file to the input file. So this is the basic strategy of this answer!
I decided to add this answer because apparently the other answers don't work on most browsers or guaranteed on mobile devices.
Briefly the code is based on 3 points:
The input file is initially created dynamically in "memory" in js
(we don't add it to the "HTML" at this moment);
After adding the file then the input file is added to the HTML, otherwise nothing occurs;
The removal of the file is done by removing the input file from the
HTML by a specific event, which means that the
"editing"/"modification" of the file is done by removing the old
input file and creating a new one.
For a better understanding look at the code below and the notes as well.
[...]
<button type="button" onclick="addIptFl();">ADD INPUT FILE!</button>
<span id="ipt_fl_parent"></span>
[...]
function dynIptFl(jqElInst, funcsObj) {
if (typeof funcsObj === "undefined" || funcsObj === "") {
funcsObj = {};
}
if (funcsObj.hasOwnProperty("before")) {
if (!funcsObj["before"].hasOwnProperty("args")) {
funcsObj["before"]["args"] = [];
}
funcsObj["before"]["func"].apply(this, funcsObj["before"]["args"]);
}
var jqElInstFl = jqElInst.find("input[type=file]");
// NOTE: Open the file selection box via js. By Questor
jqElInstFl.trigger("click");
// NOTE: This event is triggered if the user selects a file. By Questor
jqElInstFl.on("change", {funcsObj: funcsObj}, function(e) {
// NOTE: With the strategy below we avoid problems with other unwanted events
// that may be associated with the DOM element. By Questor
e.preventDefault();
var funcsObj = e.data.funcsObj;
if (funcsObj.hasOwnProperty("after")) {
if (!funcsObj["after"].hasOwnProperty("args")) {
funcsObj["after"]["args"] = [];
}
funcsObj["after"]["func"].apply(this, funcsObj["after"]["args"]);
}
});
}
function remIptFl() {
// NOTE: Remove the input file. By Questor
$("#ipt_fl_parent").empty();
}
function addIptFl() {
function addBefore(someArgs0, someArgs1) {
// NOTE: All the logic here happens just before the file selection box opens.
// By Questor
// SOME CODE HERE!
}
function addAfter(someArgs0, someArgs1) {
// NOTE: All the logic here happens only if the user adds a file. By Questor
// SOME CODE HERE!
$("#ipt_fl_parent").prepend(jqElInst);
}
// NOTE: The input file is hidden as all manipulation must be done via js.
// By Questor
var jqElInst = $('\
<span>\
<button type="button" onclick="remIptFl();">REMOVE INPUT FILE!</button>\
<input type="file" name="input_fl_nm" style="display: block;">\
</span>\
');
var funcsObj = {
before: {
func: addBefore,
args: [someArgs0, someArgs1]
},
after: {
func: addAfter,
// NOTE: The instance with the input file ("jqElInst") could be passed
// here instead of using the context of the "addIptFl()" function. That
// way "addBefore()" and "addAfter()" will not need to be inside "addIptFl()",
// for example. By Questor
args: [someArgs0, someArgs1]
}
};
dynIptFl(jqElInst, funcsObj);
}
Thanks! =D
We achieved in angular like below.
bind click event on input type file.
Attach focus event with window and add condition if uploadPanel is true then show console.
when click on input type file the boolean uploadPanel value is true. and dialogue box appear.
when cancel OR Esc button click then dialogue box dispensary and console appear.
HTML
<input type="file" formControlName="FileUpload" click)="handleFileInput($event.target.files)" />
/>
TS
this.uploadPanel = false;
handleFileInput(files: FileList) {
this.fileToUpload = files.item(0);
console.log("ggg" + files);
this.uploadPanel = true;
}
#HostListener("window:focus", ["$event"])
onFocus(event: FocusEvent): void {
if (this.uploadPanel == true) {
console.log("cancel clicked")
this.addSlot
.get("FileUpload")
.setValidators([
Validators.required,
FileValidator.validate,
requiredFileType("png")
]);
this.addSlot.get("FileUpload").updateValueAndValidity();
}
}
Just add 'change' listener on your input whose type is file. i.e
<input type="file" id="file_to_upload" name="file_to_upload" />
I have done using jQuery and obviously anyone can use valina JS (as per the requirement).
$("#file_to_upload").change(function() {
if (this.files.length) {
alert('file choosen');
} else {
alert('file NOT choosen');
}
});
TL;DR: Trying to fire a manual javascript click event on the chat button of twitch, won't send the message. Don't understand why the event doesn't do the same as a normal click and don't know how to make it work.
So I am trying to make a custom bot for twitch.tv, only reading his info from the HTML directly. I've got it perfectly working up to the point at where it can recognize commands and put text in the textbox. Now the problem I have is, as soon as I try to fire a manual click event on the "chat" button, it just doesn't seem to work. My guess is it has something to do with ember.js, and I frankly don't know anything about that. Anyway, here is the part of the code that doesn't work. EDIT: this works if I enter it as single in the console, doesn't work in context of the rest of my code though.
$('.send-chat-button').click();
What happens here is that I acquire a piece of html that contains the chat submit button, which is this:
<button class="button primary float-right send-chat-button" data-bindattr-3945="3945">
<span>
Chat
</span>
</button>
When I try to manually fire a click event on this, nothing happens. However, when I fire a manual click event on buttonContain.children[0] and buttonContain.children1 (which are, respectively, the settings and list of viewers buttons), it does work. They look like this:
<a data-ember-action="3943" class="button glyph-only float-left" title="Chat Settings"></a>
I'm guessing the difference is in the data-ember-action and the data-bindattr-*, but I don't know how to make it work. Anyone here knows why the click() event doesn't work and directly clicking does?
EDIT: If you have any questions about my question, feel free to ask.
EDIT2: I experimented a little more, and I can remove all HTML attributes from the button, and clicking on it will still work. I have no idea what is going on :(.
EDIT3: Okay, so it seems it only stops working when i remove the
Span within the button
Still no idea what is going on. (Yes, have also tried to fire the click event on the span)
EDIT4: As requested, here is all the code from my side. Note that I'm trying to click a button from twitch itself, of which ember side I do not own any code. This code is used by pasting it in the console on a twitch.tv stream and then starting it by calling initiateMessageProcessing. I'm sorry for the lot of hardcoded values, those are twitch' fields that I need. For now I'm just looking for a proof of concept.
var frequency = 5000;
var myInterval = 0;
var lastMessageId = 0;
function initiateMessageProcessing() {
if (myInterval > 0) {
clearInterval(myInterval);
}
myInterval = setInterval("checkMessages()", frequency);
}
function checkMessages() {
var chat = document.getElementsByClassName("chat-lines")[0];
processMessages(extractUnprocessedMessages(chat.children));
lastMessageId = parseInt(chat.lastElementChild.getAttribute("id").substring(5, 10));
}
function extractUnprocessedMessages(chat) {
var unprocessedMessages = [];
var chatId = 0;
for ( i = 0; i < chat.length; i++) {
chatId = parseInt(chat[i].getAttribute("id").substring(5, 10));
if (chatId > lastMessageId) {
unprocessedMessages.push(chat[i]);
}
}
return unprocessedMessages;
}
function processMessages(unprocessedMessages) {
var messageElement;
for ( i = 0; i < unprocessedMessages.length; i++) {
messageElement = unprocessedMessages[i].children[0].getElementsByClassName("message")[0];
if (messageElement != undefined && messageElement != null) {
if (messageElement.innerHTML.search("!test") !== -1) {
sendMessage('Hello world!');
}
}
}
}
function sendMessage(message) {
fillTextArea(message);
var button = $('.send-chat-button').get(0);
var event = new MouseEvent('click', {
bubbles : true
});
button.dispatchEvent(event);
}
function fillTextArea(message){
var textArea;
var chatInterface = document.getElementsByClassName("chat-interface")[0];
var textAreaContain = chatInterface.children[0];
textArea = textAreaContain.children[0].children[0];
textArea.value = message;
}
EDIT5: Eventlistener screenshot:
EDIT6: Edited source code to use $('.send-chat-button').click();
I have tried this, does not work in the current code, it does work if I manually fire this single command in the console when there is text in the chat. But sadly does not work in my code.
EDIT7: used Ember.run, still doesn't work.
EDIT8: used dispatchmouseevent, still doesn't work in context of code
It seems that the target site attaches event listeners without help of JQuery. If it is so, you cannot trigger it using jquery .click() method.
You can try directly mocking the browser event like this:
var button = $('.send-chat-button').get(0);
var event = new MouseEvent('click', {bubbles: true});
button.dispatchEvent(event);
This code will not work in IE8 and lower, but I guess it is not your case.
I know this post is quite old but I had been looking for an answer on this for a while and nothing really worked, after trying out A LOT of stuff I found it works when you focus the chatbox first then focus the button then triggering the click event!!! uuuhm yeah...
$('.chat_text_input').focus();
$('.send-chat-button').focus().trigger('click');
I have no idea why this works (and why it doesn't in any other way), but leaving any of the focusses out makes it fail or bug out.
Programmatically clicking a DOM element to make some action done is somewhat a wrong approach.
You should have define a method myAction() which will be called in two ways. First, from your ember action triggerMyAction() and second, after listening to a custom event, "myEvent".
Instead of $('.send-chat-button').click(); you will code $('something').trigger("myEvent") then.
Something like:
Em.Controller.extend({
myAction:function(){
//do your stuff
},
onMyEvent:function(){
$('something').on('myEvent',this.myAction);
}.on('didInsertElement'),
actions:{
triggerMyAction:function(){
this.myAction();
}
}
})
Here in stackoverflow, if you started to make changes then you attempt to navigate away from the page, a javascript confirm button shows up and asks: "Are you sure you want to navigate away from this page?" blee blah bloo...
Has anyone implemented this before, how do I track that changes were committed?
I believe I could do this myself, I am trying to learn the good practices from you the experts.
I tried the following but still doesn't work:
<html>
<body>
<p>Close the page to trigger the onunload event.</p>
<script type="text/javascript">
var changes = false;
window.onbeforeunload = function() {
if (changes)
{
var message = "Are you sure you want to navigate away from this page?\n\nYou have started writing or editing a post.\n\nPress OK to continue or Cancel to stay on the current page.";
if (confirm(message)) return true;
else return false;
}
}
</script>
<input type='text' onchange='changes=true;'> </input>
</body>
</html>
Can anyone post an example?
Update (2017)
Modern browsers now consider displaying a custom message to be a security hazard and it has therefore been removed from all of them. Browsers now only display generic messages. Since we no longer have to worry about setting the message, it is as simple as:
// Enable navigation prompt
window.onbeforeunload = function() {
return true;
};
// Remove navigation prompt
window.onbeforeunload = null;
Read below for legacy browser support.
Update (2013)
The orginal answer is suitable for IE6-8 and FX1-3.5 (which is what we were targeting back in 2009 when it was written), but is rather out of date now and won't work in most current browsers - I've left it below for reference.
The window.onbeforeunload is not treated consistently by all browsers. It should be a function reference and not a string (as the original answer stated) but that will work in older browsers because the check for most of them appears to be whether anything is assigned to onbeforeunload (including a function that returns null).
You set window.onbeforeunload to a function reference, but in older browsers you have to set the returnValue of the event instead of just returning a string:
var confirmOnPageExit = function (e)
{
// If we haven't been passed the event get the window.event
e = e || window.event;
var message = 'Any text will block the navigation and display a prompt';
// For IE6-8 and Firefox prior to version 4
if (e)
{
e.returnValue = message;
}
// For Chrome, Safari, IE8+ and Opera 12+
return message;
};
You can't have that confirmOnPageExit do the check and return null if you want the user to continue without the message. You still need to remove the event to reliably turn it on and off:
// Turn it on - assign the function that returns the string
window.onbeforeunload = confirmOnPageExit;
// Turn it off - remove the function entirely
window.onbeforeunload = null;
Original answer (worked in 2009)
To turn it on:
window.onbeforeunload = "Are you sure you want to leave?";
To turn it off:
window.onbeforeunload = null;
Bear in mind that this isn't a normal event - you can't bind to it in the standard way.
To check for values? That depends on your validation framework.
In jQuery this could be something like (very basic example):
$('input').change(function() {
if( $(this).val() != "" )
window.onbeforeunload = "Are you sure you want to leave?";
});
The onbeforeunload Microsoft-ism is the closest thing we have to a standard solution, but be aware that browser support is uneven; e.g. for Opera it only works in version 12 and later (still in beta as of this writing).
Also, for maximum compatibility, you need to do more than simply return a string, as explained on the Mozilla Developer Network.
Example: Define the following two functions for enabling/disabling the navigation prompt (cf. the MDN example):
function enableBeforeUnload() {
window.onbeforeunload = function (e) {
return "Discard changes?";
};
}
function disableBeforeUnload() {
window.onbeforeunload = null;
}
Then define a form like this:
<form method="POST" action="" onsubmit="disableBeforeUnload();">
<textarea name="text"
onchange="enableBeforeUnload();"
onkeyup="enableBeforeUnload();">
</textarea>
<button type="submit">Save</button>
</form>
This way, the user will only be warned about navigating away if he has changed the text area, and will not be prompted when he's actually submitting the form.
To make this work in Chrome and Safari, you would have to do it like this
window.onbeforeunload = function(e) {
return "Sure you want to leave?";
};
Reference: https://developer.mozilla.org/en/DOM/window.onbeforeunload
With JQuery this stuff is pretty easy to do. Since you can bind to sets.
Its NOT enough to do the onbeforeunload, you want to only trigger the navigate away if someone started editing stuff.
jquerys 'beforeunload' worked great for me
$(window).bind('beforeunload', function(){
if( $('input').val() !== '' ){
return "It looks like you have input you haven't submitted."
}
});
This is an easy way to present the message if any data is input into the form, and not to show the message if the form is submitted:
$(function () {
$("input, textarea, select").on("input change", function() {
window.onbeforeunload = window.onbeforeunload || function (e) {
return "You have unsaved changes. Do you want to leave this page and lose your changes?";
};
});
$("form").on("submit", function() {
window.onbeforeunload = null;
});
})
To expand on Keith's already amazing answer:
Custom warning messages
To allow custom warning messages, you can wrap it in a function like this:
function preventNavigation(message) {
var confirmOnPageExit = function (e) {
// If we haven't been passed the event get the window.event
e = e || window.event;
// For IE6-8 and Firefox prior to version 4
if (e)
{
e.returnValue = message;
}
// For Chrome, Safari, IE8+ and Opera 12+
return message;
};
window.onbeforeunload = confirmOnPageExit;
}
Then just call that function with your custom message:
preventNavigation("Baby, please don't go!!!");
Enabling navigation again
To re-enable navigation, all you need to do is set window.onbeforeunload to null. Here it is, wrapped in a neat little function that can be called anywhere:
function enableNavigation() {
window.onbeforeunload = null;
}
Using jQuery to bind this to form elements
If using jQuery, this can easily be bound to all of the elements of a form like this:
$("#yourForm :input").change(function() {
preventNavigation("You have not saved the form. Any \
changes will be lost if you leave this page.");
});
Then to allow the form to be submitted:
$("#yourForm").on("submit", function(event) {
enableNavigation();
});
Dynamically-modified forms:
preventNavigation() and enableNavigation() can be bound to any other functions as needed, such as dynamically modifying a form, or clicking on a button that sends an AJAX request. I did this by adding a hidden input element to the form:
<input id="dummy_input" type="hidden" />
Then any time I want to prevent the user from navigating away, I trigger the change on that input to make sure that preventNavigation() gets executed:
function somethingThatModifiesAFormDynamically() {
// Do something that modifies a form
// ...
$("#dummy_input").trigger("change");
// ...
}
The standard states that prompting can be controlled by canceling the beforeunload event or setting the return value to a non-null value. It also states that authors should use Event.preventDefault() instead of returnValue, and the message shown to the user is not customizable.
As of 69.0.3497.92, Chrome has not met the standard. However, there is a bug report filed, and a review is in progress. Chrome requires returnValue to be set by reference to the event object, not the value returned by the handler.
It is the author's responsibility to track whether changes have been made; it can be done with a variable or by ensuring the event is only handled when necessary.
window.addEventListener('beforeunload', function (e) {
// Cancel the event as stated by the standard.
e.preventDefault();
// Chrome requires returnValue to be set.
e.returnValue = '';
});
window.location = 'about:blank';
When the user starts making changes to the form, a boolean flag will be set. If the user then tries to navigate away from the page, you check that flag in the window.onunload event. If the flag is set, you show the message by returning it as a string. Returning the message as a string will popup a confirmation dialog containing your message.
If you are using ajax to commit the changes, you can set the flag to false after the changes have been committed (i.e. in the ajax success event).
Here try this it works 100%
<html>
<body>
<script>
var warning = true;
window.onbeforeunload = function() {
if (warning) {
return "You have made changes on this page that you have not yet confirmed. If you navigate away from this page you will lose your unsaved changes";
}
}
$('form').submit(function() {
window.onbeforeunload = null;
});
</script>
</body>
</html>
You can add an onchange event on the textarea (or any other fields) that set a variable in JS. When the user attempts to close the page (window.onunload) you check the value of that variable and show the alert accordingly.
Based on all the answers on this thread, I wrote the following code and it worked for me.
If you have only some input/textarea tags which requires an onunload event to be checked, you can assign HTML5 data-attributes as data-onunload="true"
for eg.
<input type="text" data-onunload="true" />
<textarea data-onunload="true"></textarea>
and the Javascript (jQuery) can look like this :
$(document).ready(function(){
window.onbeforeunload = function(e) {
var returnFlag = false;
$('textarea, input').each(function(){
if($(this).attr('data-onunload') == 'true' && $(this).val() != '')
returnFlag = true;
});
if(returnFlag)
return "Sure you want to leave?";
};
});
here is my html
<!DOCTYPE HMTL>
<meta charset="UTF-8">
<html>
<head>
<title>Home</title>
<script type="text/javascript" src="script.js"></script>
</head>
<body onload="myFunction()">
<h1 id="belong">
Welcome To My Home
</h1>
<p>
<a id="replaceME" onclick="myFunction2(event)" href="https://www.ccis.edu">I am a student at Columbia College of Missouri.</a>
</p>
</body>
And so this is how I did something similar in javaScript
var myGlobalNameHolder ="";
function myFunction(){
var myString = prompt("Enter a name", "Name Goes Here");
myGlobalNameHolder = myString;
if (myString != null) {
document.getElementById("replaceME").innerHTML =
"Hello " + myString + ". Welcome to my site";
document.getElementById("belong").innerHTML =
"A place you belong";
}
}
// create a function to pass our event too
function myFunction2(event) {
// variable to make our event short and sweet
var x=window.onbeforeunload;
// logic to make the confirm and alert boxes
if (confirm("Are you sure you want to leave my page?") == true) {
x = alert("Thank you " + myGlobalNameHolder + " for visiting!");
}
}
From the WebAPIs->WindowEventHandler->onbeforeunload, it recommends use window.addEventListener() and the beforeunload event, instead of onbeforeunload.
Syntax example
window.addEventListener("beforeunload", function(event) { ... });
window.onbeforeunload = function(event) { ... };
Note: The HTML specification states that authors should use the Event.preventDefault() method instead of using Event.returnValue to prompt the user.
So, in terms of your case, the code should look like this:
//javascript
window..addEventListener("beforeunload", function(event) {
//your code
// If you prevent default behaviour in Mozilla Firefox prompt will always be shown
e.preventDefault();
// Chrome requires returnValue to be set
e.returnValue = '';
})
It can be easily done by setting a ChangeFlag to true, on onChange event of TextArea. Use javascript to show confirm dialog box based on the ChangeFlag value. Discard the form and navigate to requested page if confirm returns true, else do-nothing.
What you want to use is the onunload event in JavaScript.
Here is an example: http://www.w3schools.com/jsref/event_onunload.asp
There is an "onunload" parameter for the body tag you can call javascript functions from there. If it returns false it prevents navigating away.