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You can't.

The result of the file dialog is not exposed to the browser.

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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.

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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>

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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.

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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

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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.

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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.

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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

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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.

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I needed to do it and I ended up creating a very simple solution. Can be seen here: http://jsfiddle.net/elizeubh2006/1w711q0y/5/

(But will only work after a first file selection has occurred. For me it was useful because the onchange event was being called even when the user clicked cancel. The user chose a file, then clicked to select another file, but canceled and the onchange was called.)

   $("#inputFileId").on("change", function() {
var x = document.getElementById('inputFileId');
if(x.files.length == 0)
{
alert('cancel was pressed');
}
else
{
alert(x.files[0].name);
}


});

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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);
});

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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.

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/* 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 */
}
});

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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);
};
});

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You can make a jquery change listener on the input field and detect that user cancel or closed upload window by the value of the field.

here is an example:

//when upload button change
$('#upload_btn').change(function(){
//get uploaded file
var file = this.files[0];


//if user choosed a file
if(file){
//upload file or perform your desired functiuonality
}else{
//user click cancel or close the upload window
}
});

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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) {
// ...
}

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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.

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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.

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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.

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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.

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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/

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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
}
});

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//Use hover instead of blur

var fileInput = $("#fileInput");


if (fileInput.is(":hover") {


//open
} else {


}

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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*.

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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.

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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.

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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();

});

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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 ...
}

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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

小开

We achieved in angular like below.

1. bind click event on input type file.
  1. Attach focus event with window and add condition if uploadPanel is true then show console.
  2. when click on input type file the boolean uploadPanel value is true. and dialogue box appear.
  3. 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();
}
}

小开

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');


}


});

小开

    enter code here
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta http-equiv="X-UA-Compatible" content="ie=edge" />
<title>Document</title>
</head>
<body>
<h1>Hello</h1>
<div id="cancel01">
<button>Cancel</button>
</div>


<div id="cancel02">
<button>Cancel</button>
</div>


<div id="cancel03">
<button>Cancel</button>
</div>


<form>
<input type="file" name="name" placeholder="Name" />
</form>


<script>
const nameInput = document.querySelector('input[type="file"]');


/******
*The below code if for How to detect when cancel is clicked on file input
******/
nameInput.addEventListener('keydown', e => {
/******
*If the cancel button is clicked,then you should change the input file value to empty
******/


if (e.key == 'Backspace' || e.code == 'Backspace' || e.keyCode == 8) {
console.log(e);


/******
*The below code will delete the file path
******/
nameInput.value = '';
}
});
</script>
</body>
</html>

小开

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.

小开

A lot of people keep suggesting the change event... even though OP specified that this doesn't work in the question:

CLICKING CANCEL DOES NOT SELECT A FILE AND THUS WILL NOT TRIGGER A CHANGE TO FILE INPUT!!!

all the code most people are suggesting will NOT run when cancel is clicked.

After a lot of experimentation based on suggestions from people who actually read OP's question, I've come up with this class to wrap the functionality of the file input and added two custom events:

choose: The user has chosen a file (still triggers if they select the same file again).
cancel: The user has clicked cancel or otherwise closed the file dialog with no selection.

I've also added redundancy (listen to multiple events to try and determine if cancel was pressed). Might not always respond right away but should at least guarantee that a cancel event is registered when the user re-engages the page.

Finally I noticed that events are not always guaranteed to happen in the same order (especially when the dialog closing triggers them all at nearly the same instant). This class waits for 100ms to make sure that the change event has fired before it checks for a success flag.

Uses ES6 class so probably won't work for anything before that FYI, though you could probably edit it if you wanna waste your time making it work on IE 😝.

The Class:

class FileManager {
// Keep important properties from being overwritten
constructor() {
Object.defineProperties(this, {
// The file input element (hidden)
_fileInput: {
value: document.createElement('input'),
writeable: false,
enumerable: false,
configurable: false
},
// Flag to denote if a file was chosen
_chooseSuccess: {
value: false,
writable: true,
},
// Keeps events from mult-firing
// Don't want to consume just incase!
_eventFiredOnce: {
value: false,
writable: true,
},
// Called BEFORE dialog is shown
_chooseStart_handler: {
value: (event) => {
// Choose might happen, assume it won't
this._chooseSuccess = false;


// Allow a single fire
this._eventFiredOnce = false;


// Reset value so repeat files also trigger a change/choose
this._fileInput.value = '';






/* File chooser is semi-modal and will stall events while it's opened */
/* Beware, some code can still run while the dialog is opened! */


// Window will usually focus on dialog close
// If it works this is best becuase the event will trigger as soon as the dialog is closed
// Even the user has moved the dialog off of the browser window is should still refocus
window.addEventListener('focus', this._chooseEnd_handler);


// This will always fire when the mouse first enters the body
// A good redundancy but will not fire immeditely if the cance button is not...
// in window when clicked
document.body.addEventListener('mouseenter', this._chooseEnd_handler);


// Again almost a guarantee that this will fire but it will not do so...
// imediately if the dialog is out of window!
window.addEventListener('mousemove', this._chooseEnd_handler);
},
writeable: false,
enumerable: false,
configurable: false
},
_chooseEnd_handler: {
// Focus event may beat change event
// Wait 1/10th of a second to make sure change registers!
value: (event) => {
// queue one event to fire
if (this._eventFiredOnce)
return;


// Mark event as fired once
this._eventFiredOnce = true;
// double call prevents 'this' context swap, IHT!
setTimeout((event) => {
this._timeout_handler(event);
}, 100);
},
writeable: false,
enumerable: false,
configurable: false
},
_choose_handler: {
value: (event) => {
// A file was chosen by the user
// Set flag
this._chooseSuccess = true;
// End the choose
this._chooseEnd_handler(event);
},
writeable: false,
enumerable: false,
configurable: false
},
_timeout_handler: {
value: (event) => {
if (!this._chooseSuccess) {
// Choose process done, no file selected
// Fire cancel event on input
this._fileInput.dispatchEvent(new Event('cancel'));
} else {
// Choose process done, file was selected
// Fire chosen event on input
this._fileInput.dispatchEvent(new Event('choose'));
}


// remove listeners or cancel will keep firing
window.removeEventListener('focus', this._chooseEnd_handler);
document.body.removeEventListener('mouseenter', this._chooseEnd_handler);
window.removeEventListener('mousemove', this._chooseEnd_handler);
},
writeable: false,
enumerable: false,
configurable: false
},
addEventListener: {
value: (type, handle) => {
this._fileInput.addEventListener(type, handle);
},
writeable: false,
enumerable: false,
configurable: false
},
removeEventListener: {
value: (type, handle) => {
this._fileInput.removeEventListener(type, handle);
},
writeable: false,
enumerable: false,
configurable: false
},
// Note: Shadow clicks must be called from a user input event stack!
openFile: {
value: () => {
// Trigger custom pre-click event
this._chooseStart_handler();


// Show file dialog
this._fileInput.click();
// ^^^ Code will still run after this part (non halting)
// Events will not trigger though until the dialog is closed
}
}
});
this._fileInput.type = 'file';
this._fileInput.addEventListener('change', this._choose_handler);
}


// Get all files
get files() {
return this._input.files;
}


// Get input element (reccomended to keep hidden);
get domElement(){
return this._fileInput;
}


// Get specific file
getFile(index) {
return index === undefined ? this._fileInput.files[0] : this._fileInput.files[index];
}


// Set multi-select
set multiSelect(value) {
let val = value ? 'multiple' : '';
this._fileInput.setAttribute('multiple', val);
}


// Get multi-select
get multiSelect() {
return this._fileInput.multiple === 'multiple' ? true : false;
}
}

Usage Example:

// Instantiate
let fm = new FileManager();


// Bind to something that triggers a user input event (buttons are good)
let btn = document.getElementById('btn');


// Call openFile on intance to show the dialog to the user
btn.addEventListener('click', (event) => {
fm.openFile();
});


// Fires if the user selects a file and clicks the 'okay' button
fm.addEventListener('choose', (event) => {
console.log('file chosen: ' + fm.getFile(0).name);
});


// Fires if the user clicks 'cancel' or closes the file dialog
fm.addEventListener('cancel', (event) => {
console.log('File choose has been canceled!');
});

Might be very late but I think this is a decent solution that covers most of the crippling edge cases. I'll be using this solution myself so I might come back with a git repo eventually after I play with it and refine it more.

How to detect when cancel is clicked on file input?