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<a> element does not recognize the file extension automatically when downloading a file

I'm currently developing an application where the user clicks on an element, that element calls a JS function and the function handles a file download.
The files are reports generated dynamically by Devexpress XtraReports module, converted to Base64 and then sent back to the client side. When the client receives the Base64 string, the JS function creates an <a> element, sets the href attribute to data:application/pdf;base64,JVBERi0xLjQNCiWio[...] and simulates a click with the click() event.
Here's the piece of JS code that handles the file download:
let downloadLink;
try {
downloadLink = executionId ? await getLinkPdfBase64(executionId) : false;
} catch (error) {
downloadLink = false;
console.log(error);
}
if (downloadLink) {
const aElement = document.createElement("a");
downloadLink = "data:application/pdf;base64," + downloadLink;
aElement.setAttribute("download", currentReportData.LayoutName);
aElement.setAttribute("href", downloadLink);
aElement.click();
aElement.remove();
} else {
DevExpress.ui.dialog.alert( //Ignore this, it's a Devexpress component
"Your report could not be generated",
"Alert"
);
}
The problem is:
When I generate a report with custom parameter types, Devexpress generates it correctly (the Base64, if converted to string, is visibly correctly formed) but the browser (Google Chrome) downloads the file with the extension ".0".
If the report has normal Devexpress parameters (like Strings, Int32, Guids, etc)) the file is downloaded with the correct ".pdf" extension.
Here's a picture of a correctly downloaded PDF and a ".0" extension file:
Could it be the JS function the cause or the solution to the problem? If not, almost for sure there will be something wrong with the report generator (Devexpress).
NB: If I manually change the ".0" extension to ".pdf" the file opens and it is displayed / formed correctly.

Turns out I ended up solving it just by adding the file extension ".pdf" in the download attribute, so when the browser can't recognize it, you are already specifying which one it is:
aElement.setAttribute("download", currentReportData.LayoutName + ".pdf");

Can I set the filename of a PDF object displayed in Chrome?

In my Vue app I receive a PDF as a blob, and want to display it using the browser's PDF viewer.
I convert it to a file, and generate an object url:
const blobFile = new File([blob], `my-file-name.pdf`, { type: 'application/pdf' })
this.invoiceUrl = window.URL.createObjectURL(blobFile)
Then I display it by setting that URL as the data attribute of an object element.
<object
:data="invoiceUrl"
type="application/pdf"
width="100%"
style="height: 100vh;">
</object>
The browser then displays the PDF using the PDF viewer. However, in Chrome, the file name that I provide (here, my-file-name.pdf) is not used: I see a hash in the title bar of the PDF viewer, and when I download the file using either 'right click -> Save as...' or the viewer's controls, it saves the file with the blob's hash (cda675a6-10af-42f3-aa68-8795aa8c377d or similar).
The viewer and file name work as I'd hoped in Firefox; it's only Chrome in which the file name is not used.
Is there any way, using native Javascript (including ES6, but no 3rd party dependencies other than Vue), to set the filename for a blob / object element in Chrome?
[edit] If it helps, the response has the following relevant headers:
Content-Type: application/pdf; charset=utf-8
Transfer-Encoding: chunked
Content-Disposition: attachment; filename*=utf-8''Invoice%2016246.pdf;
Content-Description: File Transfer
Content-Encoding: gzip

Chrome's extension seems to rely on the resource name set in the URI, i.e the file.ext in protocol://domain/path/file.ext.
So if your original URI contains that filename, the easiest might be to simply make your <object>'s data to the URI you fetched the pdf from directly, instead of going the Blob's way.
Now, there are cases it can't be done, and for these, there is a convoluted way, which might not work in future versions of Chrome, and probably not in other browsers, requiring to set up a Service Worker.
As we first said, Chrome parses the URI in search of a filename, so what we have to do, is to have an URI, with this filename, pointing to our blob:// URI.
To do so, we can use the Cache API, store our File as Request in there using our URL, and then retrieve that File from the Cache in the ServiceWorker.
Or in code,
From the main page
// register our ServiceWorker
navigator.serviceWorker.register('/sw.js')
.then(...
...
async function displayRenamedPDF(file, filename) {
// we use an hard-coded fake path
// to not interfere with legit requests
const reg_path = "/name-forcer/";
const url = reg_path + filename;
// store our File in the Cache
const store = await caches.open( "name-forcer" );
await store.put( url, new Response( file ) );
const frame = document.createElement( "iframe" );
frame.width = 400
frame.height = 500;
document.body.append( frame );
// makes the request to the File we just cached
frame.src = url;
// not needed anymore
frame.onload = (evt) => store.delete( url );
}
In the ServiceWorker sw.js
self.addEventListener('fetch', (event) => {
event.respondWith( (async () => {
const store = await caches.open("name-forcer");
const req = event.request;
const cached = await store.match( req );
return cached || fetch( req );
})() );
});
Live example (source)
Edit: This actually doesn't work in Chrome...
While it does set correctly the filename in the dialog, they seem to be unable to retrieve the file when saving it to the disk...
They don't seem to perform a Network request (and thus our SW isn't catching anything), and I don't really know where to look now.
Still this may be a good ground for future work on this.
And an other solution, I didn't took the time to check by myself, would be to run your own pdf viewer.
Mozilla has made its js based plugin pdf.js available, so from there we should be able to set the filename (even though once again I didn't dug there yet).
And as final note, Firefox is able to use the name property of a File Object a blobURI points to.
So even though it's not what OP asked for, in FF all it requires is
const file = new File([blob], filename);
const url = URL.createObjectURL(file);
object.data = url;

In Chrome, the filename is derived from the URL, so as long as you are using a blob URL, the short answer is "No, you cannot set the filename of a PDF object displayed in Chrome." You have no control over the UUID assigned to the blob URL and no way to override that as the name of the page using the object element. It is possible that inside the PDF a title is specified, and that will appear in the PDF viewer as the document name, but you still get the hash name when downloading.
This appears to be a security precaution, but I cannot say for sure.
Of course, if you have control over the URL, you can easily set the PDF filename by changing the URL.

I believe Kaiido's answer expresses, briefly, the best solution here:
"if your original URI contains that filename, the easiest might be to simply make your object's data to the URI you fetched the pdf from directly"
Especially for those coming from this similar question, it would have helped me to have more description of a specific implementation (working for pdfs) that allows the best user experience, especially when serving files that are generated on the fly.
The trick here is using a two-step process that perfectly mimics a normal link or button click. The client must (step 1) request the file be generated and stored server-side long enough for the client to (step 2) request the file itself. This requires you have some mechanism supporting unique identification of the file on disk or in a cache.
Without this process, the user will just see a blank tab while file-generation is in-progress and if it fails, then they'll just get the browser's ERR_TIMED_OUT page. Even if it succeeds, they'll have a hash in the title bar of the PDF viewer tab, and the save dialog will have the same hash as the suggested filename.
Here's the play-by-play to do better:
You can use an anchor tag or a button for the "download" or "view in browser" elements
Step 1 of 2 on the client: that element's click event can make a request for the file to be generated only (not transmitted).
Step 1 of 2 on the server: generate the file and hold on to it. Return only the filename to the client.
Step 2 of 2 on the client:
If viewing the file in the browser, use the filename returned from the generate request to then invoke window.open('view_file/<filename>?fileId=1'). That is the only way to indirectly control the name of the file as shown in the tab title and in any subsequent save dialog.
If downloading, just invoke window.open('download_file?fileId=1').
Step 2 of 2 on the server:
view_file(filename, fileId) handler just needs to serve the file using the fileId and ignore the filename parameter. In .NET, you can use a FileContentResult like File(bytes, contentType);
download_file(fileId) must set the filename via the Content-Disposition header as shown here. In .NET, that's return File(bytes, contentType, desiredFilename);
client-side download example:
download_link_clicked() {
// show spinner
ajaxGet(generate_file_url,
{},
(response) => {
// success!
// the server-side is responsible for setting the name
// of the file when it is being downloaded
window.open('download_file?fileId=1', "_blank");
// hide spinner
},
() => { // failure
// hide spinner
// proglem, notify pattern
},
null
);
client-side view example:
view_link_clicked() {
// show spinner
ajaxGet(generate_file_url,
{},
(response) => {
// success!
let filename = response.filename;
// simplest, reliable method I know of for controlling
// the filename of the PDF when viewed in the browser
window.open('view_file/'+filename+'?fileId=1')
// hide spinner
},
() => { // failure
// hide spinner
// proglem, notify pattern
},
null
);

I'm using the library pdf-lib, you can click here to learn more about the library.
I solved part of this problem by using api Document.setTitle("Some title text you want"),
Browser displayed my title correctly, but when click the download button, file name is still previous UUID. Perhaps there is other api in the library that allows you to modify download file name.

CSV download File Name

I am trying to download a CSV file from json data stored in a variable.
The issue is that I am not able to set the name of the downloaded file.
Here is the code...
$('#downloadCSV').click(function () {
var exportData = 'data:attachment/csv;charset=utf-8,';
exportData += 'nodeid,value\n1,212\n';
var newWindow = window.open(encodeURI(exportData));
return false;
});
I have already tried to add the HTML5 download attr:
<a id="downloadCSV" download="data.csv" href="#">Download CSV</a>
I have already tried the solutions provided by others and nothing is working with the current browsers ...

I find the FileSaver library a really useful cross-browser solution for saving files from JavaScript. Their documentation provides a compatibility table which will show you which browsers support file names.
BTW the download attribute on the <a> tag is an HTML5 feature which would apply if you were linking to a file's URL directly with the href. As you are catching the click event using JavaScript, and then returning false, this will not be doing anything.

Saving file with JavaScript File API results wrong encoding

I have a problem (or may be two) with saving files using HTML5 File API.
A files comes from the server as a byte array and I need to save it. I tried several ways described on SO:
creating blob and opening it in a new tab
creating a hidden anchor tag with "data:" in href attribute
using FileSaver.js
All approaches allow to save the file but with breaking it by changing the encoding to UTF-8, while the file (in current test case) is in ANSI. And it seems that I have to problems: at the server side and at the client side.
Server side:
Server side is ASP.NET Web API 2 app, which controller sends the file using HttpResponseMessage with StreamContent. The ContentType is correct and corresponds with actual file type.
But as can be seen on the screenshot below server's answer (data.length) is less then actual file size calculated at upload (file.size). Also here could be seen that HTML5 File object has yet another size (f.size).
If I add CharSet with value "ANSI" to server's response message's ContentType property, file data will be the same as it was uploaded, but on saving result file still has wrong size and become broken:
Client side:
I tried to set charset using the JS File options, but it didn't help. As could be found here and here Eli Grey, the author of FileUplaod.js says that
The encoding/charset in the type is just metadata for the browser, not an encoding directive.
which means, if I understood it right, that it is impossible to change the encoding of the file.
Issue result: at the end I can successfully download broken files which are unable to open.
So I have two questions:
How can I save file "as is" using File API. At present time I cannot use simple way with direct link and 'download' attribute because of serverside check for access_token in request header. May be this is the "bottle neck" of the problem?
How can I avoid setting CharSet at server side and also send byte array "as is"? While this problem could be hacked in some way I guess it's more critical. For example, while "ANSI" charset solves the problem with the current file, WinMerge shows that it's encoding is Cyrillic 'Windows-1251' and also can any other.
P.S. the issue is related to all file types (extensions) except *.txt.
Update
Server side code:
public HttpResponseMessage DownloadAttachment(Guid fileId)
{
var stream = GetFileStream(fileId);
var message = new HttpResponseMessage(HttpStatusCode.OK);
message.Content = new StreamContent(stream);
message.Content.Headers.ContentLength = file.Size;
message.Content.Headers.ContentType = new MediaTypeHeaderValue(file.ContentType)
{
// without this charset files sent with bigger size
// than they are as shown on image 1
CharSet = "ANSI"
};
message.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
{
FileName = file.FileName + file.Extension,
Size = file.Size
};
return message;
}
Client side code (TypeScript):
/*
* Handler for click event on download <a> tag
*/
private downloadFile(file: Models.File) {
var self = this;
this.$service.downloadAttachment(this.entityId, file.fileId).then(
// on success
function (data, status, headers, config) {
var fileName = file.fileName + file.extension;
var clientFile = new File([data], fileName);
// here's the issue ---^
saveAs(clientFile, fileName);
},
// on fail
function (error) {
self.alertError(error);
});
}
My code is almost the same as in answers on related questions on SO: instead of setting direct link in 'a' tag, I handle click on it and download file content via XHR (in my case using Angularjs $http service). Getting the file content I create a Blob object (in my case I use File class that derives from Blob) and then try to save it using FileSaver.js. I also tried approach with encoded URL to Blob in href attribute, but it only opens a new tab with a file broken the same way. I found that the problem is in Blob class - calling it's constructor with 'normal' file data I get an instance with 'wrong' size as could be seen on first two screenshots. So, as I understand, my problem not in the way I try to save my file, but in the way I create it - File API

Reading image capture files in PhoneGap

I'm working on a PhoneGap application that captures images using the camera and, later, uploads them. There are two modes of operation for camera in PhoneGap: raw base64 encoded data or a file URI.
The docs themselves say:
Note: The image quality of pictures taken using the camera on newer
devices is quite good. Encoding such images using Base64 has caused
memory issues on some of these devices (iPhone 4, BlackBerry Torch
9800). Therefore, using FILE_URI as the 'Camera.destinationType' is
highly recommended.
So I'm keen to use FILE_URI option. This works great and you can even show the images in IMG tags. The URL looks like this:
file://localhost/var/mobile/Applications/4FE4642B-944C-449BB-9BD6-1E442E47C7CE/tmp/photo_047.jpg
However, at some point later I want to read the contents of the file to upload to a server. I was going to do this using the FileReader type. This doesn't work and I think it's because I can't access the file at the URL above.
The error code I get back from readDataUrl is 1 > FileError.NOT_FOUND_ERR = 1;
Any ideas how I can get to the file? I tried just accessing the last part of the path (photo_047.jpg) based on another sample I saw but no luck.

I'm just getting started with PhoneGap, and given the age of this question you may have found an answer already, but I'll give it a try anyway.
First, would you be able to use the built-in FileTransfer object? It takes a file: URI as an argument.
If FileTransfer won't work for you, and you need to read the file data yourself, you'll need the PhoneGap File objects, like FileReader , as you said. But most of those expect a plain pathname -- not a URI -- to specify the file to work with. The reason you're getting NOT_FOUND_ERR is because it's trying to open a file named file:/localhost/var....
Here's a quick one-liner to extract the path part from your URI:
var path = /file:\/\/.*?(\/.*)/.exec(fileuri)[1];
Hope this helps!

The answer from jgarbers was of help to me but it did not solve the problem. I realized the camera stores photos in Temp folder instead of Document folder. Setting my local file system to temporary allowed it to find the correct location for the camera images.
window.requestFileSystem(LocalFileSystem.TEMPORARY, 0, ...

...
window.requestFileSystem(LocalFileSystem.TEMPORARY, 0, ...
...
var path = /file://.?(/.)/.exec(fileuri)[1];
Ref. above jgarbers and Rik answers (solution has been tested successfully on iOs 7)

you can user the file transfer plugin for uploading any file to the server.
//// pass your file uri to the mediafie param
function uploadFile(mediaFile) {
var ft = new FileTransfer();
path = mediaFile.fullPath;
name = mediaFile.name;
////your service method url
var objUrl = http://example.com;
ft.upload(path,
objUrl,
function (result) {
alert("Success");
},
function (error) {
alert('Error uploading file ' + path + ': ' + error.code);
},
{ fileName: name });
}