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Corrupted .xlsx file from Flask web app and ajax POST request

I have a Flask web app with a URL route that receives a post request with some json, parses it to an .xlsx file, then returns the file with send_file().
Server side, I can see that the .xlsx file that is generated is correct but, once downloaded on the client side, the file is corrupted and can't be opened and is much larger than expected (201KB vs. 112KB).
I suspect it's some sort of encoding issue, but I've tried a whole bunch of stuff and can't make any headway. Can anyone help, please?
Flask route:
#app.route('/request/export_XLSX',methods=['POST'])
def request_export_XLSX():
json_model = json_util.loads(request.data.decode('ascii', 'ignore'))
xlsx_model = detox.xlsxFromJSONModel(json_model) # Returns file path
result = send_file(xlsx_model, as_attachment=True, attachment_filename=json_model['id']+'.xlsx', mimetype='application/vnd.ms-excel')
return result
JavaScript:
var exportModelExcel = function(){
var model = detox.fba.model
d3.selectAll('*').style("cursor","wait")
var modelJson = JSON.stringify(model)
$.ajax({
type: "POST",
url: "/request/export_XLSX",
data: modelJson,
success: function(d){
d3.selectAll('*').style("cursor","")
var blob = new Blob([d], {type: 'application/vnd.ms-excel'})
var link=document.createElement("a");
link.href=window.URL.createObjectURL(blob);
link.download=model.id+".xlsx";
link.click();
},
error: function(jqxhr,textStatus,errorThrown){
console.log("Error: " ,textStatus,errorThrown)
d3.selectAll('*').style("cursor","")
alert("There was an error exporting the model")
},
contentType: 'application/json',
responseType: 'blob',
processData: false,
});
}
Here's a link where you can see the good and bad .xlsx files: https://gofile.io/d/xywI1D

Well, I ended up ripping out the ajax and using an XMLHTTPRequest instead.
It works nicely and results in an uncorrupted .xlsx file. 🙂
var exportModelExcel = function(){
var model = detox.fba.model;
var modelJson = JSON.stringify(model);
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
var downloadUrl = URL.createObjectURL(xhttp.response);
var a = document.createElement("a");
document.body.appendChild(a);
a.style = "display: none";
a.href = downloadUrl;
a.download = model.id+".xlsx";
a.click();
}
};
xhttp.open("POST", "/request/export_XLSX", true);
xhttp.setRequestHeader("Content-Type", "application/json");
xhttp.responseType = "blob";
xhttp.send(modelJson);
}

Download of jQuery Ajax request contents is empty

I have a PHP file that returns output in PDF - Works fine if I access the file directly.
I'd like to retrieve the PDF file through AJAX.
In native Javascript, it works fine:
var req = new XMLHttpRequest();
req.open("POST", "./api/pdftest.php?wpid="+wpid, true);
req.responseType = "blob";
req.onreadystatechange = function ()
{
if (req.readyState === 4 && req.status === 200)
{
var blob=req.response;
var filename = "test.pdf";
var link = document.createElement('a');
link.href = window.URL.createObjectURL(blob);
link.download = "test.pdf";
link.click();
var file = new File([blob], filename, { type: 'application/force-download' });
window.open(URL.createObjectURL(file));
}
};
req.send();
But I guess I'd use jQuery to ensure cross browser compatibility (although the snippet above works in Edge, Chrome and Firefox on pc, I haven't tested it in other browsers/on other platforms)
So I tried to rewrite the function:
url='./api/pdftest.php?wpid='+wpid;
$.ajax(
{
url: url,
method: 'POST',
responseType: 'blob',
success: function(data)
{
var filename='test.pdf';
var blob=new Blob([data]);
var filename = "test.pdf";
var link = document.createElement('a');
link.href = window.URL.createObjectURL(blob);
link.download = "test.pdf";
link.click();
var file = new File([blob], filename, { type: 'application/force-download' });
window.open(URL.createObjectURL(file));
}
});
The jQuery equivalent allows me to download a PDF file but … the PDF file is empty.
So I guess I am doing something wrong, probably in the DATA to BLOB conversion. But what? I hope somebody can see what I am doing wrong.
I've been using ages on StackOverflow, read many suggestions - but didn't find any answer. I simply can't see the forest for the trees.

Looking at the documentation for the jQuery.ajax() function, we see there's no setting called responseType, so you need to use xhrFields to directly set a property of the XHR object. And, since you're only setting the URL and success callback, we can just use the shorter jquery.post() function.
So the data is returned, we make a Blob and then a URL to download it. I'm not on Windows so I can't test if that link I constructed will work as expected, but figured I'd do it the jQuery way.
var url = './api/pdftest.php?wpid=' + wpid;
$.post({
url: url,
xhrFields: {responseType: "blob"},
success: function(data) {
// don't set the MIME type to pdf or it will display
var blob = new Blob([data], {type: "application/octet-stream"});
// build a blob URL
var bloburl = window.URL.createObjectURL(blob);
// trigger download for edge
var link = $("<a>").attr({href: bloburl, download: "test.pdf"}).click();
// trigger download for other browsers
window.open(bloburl);
}
});

Probably double!
This is the solution I found thanks to Hisham at Download pdf file using jquery ajax:
First, add the following plugin that can be used to the XHR V2 capabilities missing in JQuery: https://github.com/acigna/jquery-ajax-native
Then:
url='./api/pdftest.php?wpid='+wpid;
$.ajax(
{
dataType: 'native',
url: url,
xhrFields:
{
responseType: 'blob'
},
success: function(blob)
{
var filename = "test.pdf";
var link = document.createElement('a');
link.href = window.URL.createObjectURL(blob);
link.download = "test.pdf";
link.click();
var file = new File([blob], filename, { type: 'application/force-download' });
window.open(URL.createObjectURL(file));
}
});
This seems to be working.
Note: the window.open() is to make download possible in Firefox, the link.click() method Works in Edge, Chrome and Opera
Thanks to miken32 for pointing into the right direction.

As binary data is not possible to retrieve through jQuery.ajax, Native is the only way, at least for now. The following method works in Edge, Firefox, Chrome and Opera - tested on WIndows 10.
var req = new XMLHttpRequest();
req.open("POST", "./api/pdftest.php?wpid="+wpid, true);
req.responseType = "blob";
req.onreadystatechange = function ()
{
if (req.readyState === 4 && req.status === 200)
{
var blob=req.response;
var filename = "test.pdf";
var link = document.createElement('a');
link.setAttribute("type", "hidden"); // make it hidden if needed
link.href = window.URL.createObjectURL(blob);
link.download = "test.pdf";
document.body.appendChild(link);
link.click();
link.remove();
var file = new File([blob], filename, { type: 'application/force-download' });
//window.open(URL.createObjectURL(file));
}
};
req.send();

Zip download is not happening

Hi I am new to java script, I am trying to download zip file from a web server running in http://10.1.2.137:5000/download.
When I access the URL alone in the browser as http://10.1.2.137:5000/download, te zip file is getting downloaded , but when I call from java script , the zip file is getting corrupted it seems. Not able to open the zip file with win rar.
Not sure this is the issue with CORS.
$scope.downloadData = function (){
console.log ('Entering in to Download Method')
var url = 'http://10.1.2.137:5000/download';
var xhr = new XMLHttpRequest();
xhr.open("GET", url);
xhr.setRequestHeader("Content-Type", "application/json;charset=UTF-8");
xhr.setRequestHeader("Access-Control-Allow-Origin", "*");
xhr.responseType = "arraybuffer";
var linkElement = document.createElement('iframe');
document.body.appendChild(linkElement)
xhr.send();
xhr.onreadystatechange = function() {
if (xhr.readyState == 4 && xhr.status == 200) {
var blob = new Blob([str2bytes(xhr.response)], {type: "application/zip"});
var fileName = "logs.zip";
if (window.navigator && window.navigator.msSaveOrOpenBlob) {
window.navigator.msSaveOrOpenBlob(blob, filename);
} else {
var a = document.createElement("a");
document.body.appendChild(a);
a.style = "display:none";
var url = window.URL.createObjectURL(blob);
a.href = url;
a.download = fileName;
a.click();
window.URL.revokeObjectURL(url);
a.remove();
}
}
}
};

You can use window.open, this will instruct the browser to open the url and start download. e.g.
window.open("http://10.1.2.137:5000/download","_self");

download file using an ajax request

I want to send an "ajax download request" when I click on a button, so I tried in this way:
javascript:
var xhr = new XMLHttpRequest();
xhr.open("GET", "download.php");
xhr.send();
download.php:
<?
header("Cache-Control: public");
header("Content-Description: File Transfer");
header("Content-Disposition: attachment; filename= file.txt");
header("Content-Transfer-Encoding: binary");
readfile("file.txt");
?>
but doesn't work as expected, how can I do ? Thank you in advance

Update April 27, 2015
Up and coming to the HTML5 scene is the download attribute. It's supported in Firefox and Chrome, and soon to come to IE11. Depending on your needs, you could use it instead of an AJAX request (or using window.location) so long as the file you want to download is on the same origin as your site.
You could always make the AJAX request/window.location a fallback by using some JavaScript to test if download is supported and if not, switching it to call window.location.
Original answer
You can't have an AJAX request open the download prompt since you physically have to navigate to the file to prompt for download. Instead, you could use a success function to navigate to download.php. This will open the download prompt but won't change the current page.
$.ajax({
url: 'download.php',
type: 'POST',
success: function() {
window.location = 'download.php';
}
});
Even though this answers the question, it's better to just use window.location and avoid the AJAX request entirely.

To make the browser downloads a file you need to make the request like that:
function downloadFile(urlToSend) {
var req = new XMLHttpRequest();
req.open("GET", urlToSend, true);
req.responseType = "blob";
req.onload = function (event) {
var blob = req.response;
var fileName = req.getResponseHeader("fileName") //if you have the fileName header available
var link=document.createElement('a');
link.href=window.URL.createObjectURL(blob);
link.download=fileName;
link.click();
};
req.send();
}

You actually don't need ajax at all for this. If you just set "download.php" as the href on the button, or, if it's not a link use:
window.location = 'download.php';
The browser should recognise the binary download and not load the actual page but just serve the file as a download.

Cross browser solution, tested on Chrome, Firefox, Edge, IE11.
In the DOM, add an hidden link tag:
<a id="target" style="display: none"></a>
Then:
var req = new XMLHttpRequest();
req.open("GET", downloadUrl, true);
req.responseType = "blob";
req.setRequestHeader('my-custom-header', 'custom-value'); // adding some headers (if needed)
req.onload = function (event) {
var blob = req.response;
var fileName = null;
var contentType = req.getResponseHeader("content-type");
// IE/EDGE seems not returning some response header
if (req.getResponseHeader("content-disposition")) {
var contentDisposition = req.getResponseHeader("content-disposition");
fileName = contentDisposition.substring(contentDisposition.indexOf("=")+1);
} else {
fileName = "unnamed." + contentType.substring(contentType.indexOf("/")+1);
}
if (window.navigator.msSaveOrOpenBlob) {
// Internet Explorer
window.navigator.msSaveOrOpenBlob(new Blob([blob], {type: contentType}), fileName);
} else {
var el = document.getElementById("target");
el.href = window.URL.createObjectURL(blob);
el.download = fileName;
el.click();
}
};
req.send();

It is possible. You can have the download started from inside an ajax function, for example, just after the .csv file is created.
I have an ajax function that exports a database of contacts to a .csv file, and just after it finishes, it automatically starts the .csv file download. So, after I get the responseText and everything is Ok, I redirect browser like this:
window.location="download.php?filename=export.csv";
My download.php file looks like this:
<?php
$file = $_GET['filename'];
header("Cache-Control: public");
header("Content-Description: File Transfer");
header("Content-Disposition: attachment; filename=".$file."");
header("Content-Transfer-Encoding: binary");
header("Content-Type: binary/octet-stream");
readfile($file);
?>
There is no page refresh whatsoever and the file automatically starts downloading.
NOTE - Tested in the following browsers:
Chrome v37.0.2062.120
Firefox v32.0.1
Opera v12.17
Internet Explorer v11

I prefer location.assign(url);
Complete syntax example:
document.location.assign('https://www.urltodocument.com/document.pdf');
developer.mozilla.org/en-US/docs/Web/API/Location.assign

For those looking a more modern approach, you can use the fetch API. The following example shows how to download a spreadsheet file. It is easily done with the following code.
fetch(url, {
body: JSON.stringify(data),
method: 'POST',
headers: {
'Content-Type': 'application/json; charset=utf-8'
},
})
.then(response => response.blob())
.then(response => {
const blob = new Blob([response], {type: 'application/application/vnd.openxmlformats-officedocument.spreadsheetml.sheet'});
const downloadUrl = URL.createObjectURL(blob);
const a = document.createElement("a");
a.href = downloadUrl;
a.download = "file.xlsx";
document.body.appendChild(a);
a.click();
})
I believe this approach to be much easier to understand than other XMLHttpRequest solutions. Also, it has a similar syntax to the jQuery approach, without the need to add any additional libraries.
Of course, I would advise checking to which browser you are developing, since this new approach won't work on IE. You can find the full browser compatibility list on the following link.
Important: In this example I am sending a JSON request to a server listening on the given url. This url must be set, on my example I am assuming you know this part. Also, consider the headers needed for your request to work. Since I am sending a JSON, I must add the Content-Type header and set it to application/json; charset=utf-8, as to let the server know the type of request it will receive.

#Joao Marcos solution works for me but I had to modify the code to make it work on IE, below if what the code looks like
downloadFile(url,filename) {
var that = this;
const extension = url.split('/').pop().split('?')[0].split('.').pop();
var req = new XMLHttpRequest();
req.open("GET", url, true);
req.responseType = "blob";
req.onload = function (event) {
const fileName = `${filename}.${extension}`;
const blob = req.response;
if (window.navigator.msSaveBlob) { // IE
window.navigator.msSaveOrOpenBlob(blob, fileName);
}
const link = document.createElement('a');
link.href = window.URL.createObjectURL(blob);
link.download = fileName;
link.click();
URL.revokeObjectURL(link.href);
};
req.send();
},

Decoding a filename from the header is a little bit more complex...
var filename = "default.pdf";
var disposition = req.getResponseHeader('Content-Disposition');
if (disposition && disposition.indexOf('attachment') !== -1)
{
var filenameRegex = /filename[^;=\n]*=((['"]).*?\2|[^;\n]*)/;
var matches = filenameRegex.exec(disposition);
if (matches != null && matches[1])
filename = matches[1].replace(/['"]/g, '');
}

This solution is not very different from those above, but for me it works very well and i think it's clean.
I suggest to base64 encode the file server side (base64_encode(), if you are using PHP) and send the base64 encoded data to the client
On the client you do this:
let blob = this.dataURItoBlob(THE_MIME_TYPE + "," + response.file);
let uri = URL.createObjectURL(blob);
let link = document.createElement("a");
link.download = THE_FILE_NAME,
link.href = uri;
document.body.appendChild(link);
link.click();
document.body.removeChild(link);
This code puts the encoded data in a link and simulates a click on the link, then it removes it.

Your needs are covered by
window.location('download.php');
But I think that you need to pass the file to be downloaded, not always download the same file, and that's why you are using a request, one option is to create a php file as simple as showfile.php and do a request like
var myfile = filetodownload.txt
var url = "shofile.php?file=" + myfile ;
ajaxRequest.open("GET", url, true);
showfile.php
<?php
$file = $_GET["file"]
echo $file;
where file is the file name passed via Get or Post in the request and then catch the response in a function simply
if(ajaxRequest.readyState == 4){
var file = ajaxRequest.responseText;
window.location = 'downfile.php?file=' + file;
}
}

there is another solution to download a web page in ajax. But I am referring to a page that must first be processed and then downloaded.
First you need to separate the page processing from the results download.
1) Only the page calculations are made in the ajax call.
$.post("CalculusPage.php", { calculusFunction: true, ID: 29, data1: "a", data2: "b" },
function(data, status)
{
if (status == "success")
{
/* 2) In the answer the page that uses the previous calculations is downloaded. For example, this can be a page that prints the results of a table calculated in the ajax call. */
window.location.href = DownloadPage.php+"?ID="+29;
}
}
);
// For example: in the CalculusPage.php
if ( !empty($_POST["calculusFunction"]) )
{
$ID = $_POST["ID"];
$query = "INSERT INTO ExamplePage (data1, data2) VALUES ('".$_POST["data1"]."', '".$_POST["data2"]."') WHERE id = ".$ID;
...
}
// For example: in the DownloadPage.php
$ID = $_GET["ID"];
$sede = "SELECT * FROM ExamplePage WHERE id = ".$ID;
...
$filename="Export_Data.xls";
header("Content-Type: application/vnd.ms-excel");
header("Content-Disposition: inline; filename=$filename");
...
I hope this solution can be useful for many, as it was for me.

this works for me
var dataObj = {
somekey:"someValue"
}
$.ajax({
method: "POST",
url: "/someController/someMethod",
data: dataObj,
success: function (response) {
const blob = new Blob([response], { type: 'text/csv' });
const downloadUrl = URL.createObjectURL(blob);
const a = document.createElement("a");
a.href = downloadUrl;
a.download = "file.csv";
document.body.appendChild(a);
a.click();
}
});

Downloading mp3 files using html5 blobs in a chrome-extension

I am trying to create a google-chrome-extension that will download an mp3 file. I am trying to use HTML5 blobs and an iframe to trigger a download, but it doesn't seem to be working. Here is my code:
var finalURL = "server1.example.com/u25561664/audio/120774.mp3";
var xhr = new XMLHttpRequest();
xhr.open("GET", finalURL, true);
xhr.setRequestHeader('Content-Type', 'application/octet-stream');
xhr.onreadystatechange = function()
{
if(xhr.readyState == 4 && xhr.status == 200)
{
var bb = new (window.BlobBuilder || window.WebKitBlobBuilder)();
bb.append(xhr.responseText);
var blob = bb.getBlob("application/octet-stream");
var saveas = document.createElement("iframe");
saveas.style.display = "none";
saveas.src = window.webkitURL.createObjectURL(blob);
document.body.appendChild(saveas);
delete xhr;
delete blob;
delete bb;
}
}
xhr.send();
When looked in the console, the blob is created correctly, the settings look right:
size: 15312172
type: "application/octet-stream"
However, when I try the link created by the createObjectURL(),
blob:chrome-extension://dkhkkcnjlmfnnmaobedahgcljonancbe/b6c2e829-c811-4239-bd06-8506a67cab04
I get a blank document and a warning saying
Resource interpreted as Document but
transferred with MIME type
application/octet-stream.
How can get my code to download the file correctly?

The below code worked for me in Google chrome 14.0.835.163:
var finalURL = "http://localhost/Music/123a4.mp3";
var xhr = new XMLHttpRequest();
xhr.overrideMimeType("application/octet-stream");
//xhr.setRequestHeader('Access-Control-Allow-Origin', '*');
xhr.open("GET", finalURL, true);
xhr.responseType = "arraybuffer";
xhr.onload = function() {
var bb = new (window.BlobBuilder || window.WebKitBlobBuilder)();
var res = xhr.response;
if (res){
var byteArray = new Uint8Array(res);
}
bb.append(byteArray.buffer);
var blob = bb.getBlob("application/octet-stream");
var iframe = document.createElement("iframe");
iframe.style.display = "none";
iframe.src = window.webkitURL.createObjectURL(blob);
document.body.appendChild(iframe);
};
xhr.send(null);

I'm not sure, but i think this is your server's trouble. I've just tried your piece of code to download some sample blob of mp3-file and everything went ok. So maybe:
this file doesn't exist on your server
you server outputs wrong mime type for mp3 files