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Uploading file with FormData and XmlHttpRequest with Formidable on node js backend shows empty files, fields

I am uploading a csv file using FormData and XmlHttpRequest. Here is the code for that.
I have a form wrapped around an html input type file, whose onchange event I am executing this code. I have tried to send the form directly as well and also read the form element into the FormData object.
let formData = new FormData();
let file = e.target.files[0];
var blob = new Blob([file],{type: 'text/csv'});
formData.append("payoutUpload", blob, 'processed.csv');
let uri = encodeURI(`${window.serviceUri}${path}`);
var req = new XMLHttpRequest();
req.onload = (result) => {
if (req.status === 500 && result && result.code === 'ECONNRESET') {
console.log(
'Connection was reset, hence retry the sendRequest function'
);
} else if (req.status === 200) {
} else {
console.log("Error while retrieving data");
}
}
req.onerror = (e) => {
console.log('There was an error while retrieving data from service', e);
};
req.open('POST', uri, true);
req.setRequestHeader('Content-Type', 'multipart/form-data');
req.setRequestHeader('Authorization', 'Bearer ' + token);
req.send(formData);
When I send the request, I can see that the file is being sent in the form of Request Payload.
On the NodeJs backend, I am running Express and Formidable. I am not using body-parser, I am using express's inbuilt json and urlencoding methods.
Here is the formidable part.
const form = formidable({multiples: true});
form.parse(req, (err, fields, files) => {
console.log(`error is ${JSON.stringify(err)}`);
console.log(`fields is ${JSON.stringify(fields)}`);
console.log(`files JSON: ${JSON.stringify(files)}`);
console.log('file in request: ' + files.payoutUpload);
console.log(`req.body: ${req.body}`);
options.file = files.payoutUpload;
});
I get err, fields and files as empty. I have searched through all similar questions and set the request headers correctly(which is usually the issue). I can see that the request.body still has the file payload on the server end. But formidable does not parse this. Can anyone tell what I am doing wrong?
UPDATE: I have tried other packages for parsing the file, like multer, express-fileupload, all of them return files as empty. I have also tried fetch API to send my request, but with no luck.

req.setRequestHeader('Content-Type', 'multipart/form-data')
When you send multipart/form-data you must include a boundary parameter in the header however you can't know what value you need to set for this.
Don't set the Content-Type header at all. Allow XMLHttpRequest to generate it automatically from the FormData object.

Browser Crashes when uploading large files even after slicing on XMLHttpRequest (JavaScript/ReactJS)

I've been trying to find a clear answer on this for a while now, since some have only been for big CSV files for example.
The following code works perfectly for smaller files, whenever size exceeds 100 MB, upload process takes a big chunk of memory apparently.
I'm already slicing the files into smaller chunks as well, however apparently the initial reading of the file is causing this issue.
Question: How should I change the following code to prevent the crashes to happen?
axios.post(`/URL_GOES_HERE`, {
name: file.name,
size: file.size,
md5,
extension: file.type.split('/')[1]
})
.then((response) => {
const reader = new FileReader();
reader.onload = (e) => {
const { chunks, type, status } = response.data;
if (status === 'uploading') {
let start = 0;
chunks.forEach(async ({ materialId, size, index }) => {
window.file0 = file;
const buf = reader.result.slice(start, start + size);
const arrayBuf = new Uint8Array(buf);
start = start + size;
const url = `URL_FOR_EACH_CHUNK`;
let xhr = new XMLHttpRequest();
xhr.open('PUT', url, false);
xhr.setRequestHeader(
'Content-Type',
'application/octet-stream'
);
xhr.setRequestHeader(
'Authorization',
`Bearer TOKEN_GOES_HERE`
);
xhr.send(arrayBuf);
});
}
};
reader.readAsArrayBuffer(file);
})

This is a bad way to upload files by slicing and reading the data.
just send the file as it's without reading the content
const res = await fetch('URL_GOES_HERE', {
method: 'post',
body: file
})
await res.text()
if you really need to upload them partially with chunks then just slice the blob and upload that without sending arraybuffer
chunk_to_send = file.slice(start, end)
xhr.send(chunk_to_send)
Browser will be able to pipe the data as a stream and upload them without any memory concern

Save texts from textarea as file and force browser to download [duplicate]

I have a javascript app that sends ajax POST requests to a certain URL. Response might be a JSON string or it might be a file (as an attachment). I can easily detect Content-Type and Content-Disposition in my ajax call, but once I detect that the response contains a file, how do I offer the client to download it? I've read a number of similar threads here but none of them provide the answer I'm looking for.
Please, please, please do not post answers suggesting that I shouldn't use ajax for this or that I should redirect the browser, because none of this is an option. Using a plain HTML form is also not an option. What I do need is to show a download dialog to the client. Can this be done and how?

Don't give up so quickly, because this can be done (in modern browsers) using parts of the FileAPI:
var xhr = new XMLHttpRequest();
xhr.open('POST', url, true);
xhr.responseType = 'blob';
xhr.onload = function () {
if (this.status === 200) {
var blob = this.response;
var filename = "";
var disposition = xhr.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, '');
}
if (typeof window.navigator.msSaveBlob !== 'undefined') {
// IE workaround for "HTML7007: One or more blob URLs were revoked by closing the blob for which they were created. These URLs will no longer resolve as the data backing the URL has been freed."
window.navigator.msSaveBlob(blob, filename);
} else {
var URL = window.URL || window.webkitURL;
var downloadUrl = URL.createObjectURL(blob);
if (filename) {
// use HTML5 a[download] attribute to specify filename
var a = document.createElement("a");
// safari doesn't support this yet
if (typeof a.download === 'undefined') {
window.location.href = downloadUrl;
} else {
a.href = downloadUrl;
a.download = filename;
document.body.appendChild(a);
a.click();
}
} else {
window.location.href = downloadUrl;
}
setTimeout(function () { URL.revokeObjectURL(downloadUrl); }, 100); // cleanup
}
}
};
xhr.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
xhr.send($.param(params, true));
Or if using jQuery.ajax:
$.ajax({
type: "POST",
url: url,
data: params,
xhrFields: {
responseType: 'blob' // to avoid binary data being mangled on charset conversion
},
success: function(blob, status, xhr) {
// check for a filename
var filename = "";
var disposition = xhr.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, '');
}
if (typeof window.navigator.msSaveBlob !== 'undefined') {
// IE workaround for "HTML7007: One or more blob URLs were revoked by closing the blob for which they were created. These URLs will no longer resolve as the data backing the URL has been freed."
window.navigator.msSaveBlob(blob, filename);
} else {
var URL = window.URL || window.webkitURL;
var downloadUrl = URL.createObjectURL(blob);
if (filename) {
// use HTML5 a[download] attribute to specify filename
var a = document.createElement("a");
// safari doesn't support this yet
if (typeof a.download === 'undefined') {
window.location.href = downloadUrl;
} else {
a.href = downloadUrl;
a.download = filename;
document.body.appendChild(a);
a.click();
}
} else {
window.location.href = downloadUrl;
}
setTimeout(function () { URL.revokeObjectURL(downloadUrl); }, 100); // cleanup
}
}
});

Create a form, use the POST method, submit the form - there's no need for an iframe. When the server page responds to the request, write a response header for the mime type of the file, and it will present a download dialog - I've done this a number of times.
You want content-type of application/download - just search for how to provide a download for whatever language you're using.

I faced the same issue and successfully solved it. My use-case is this.
"Post JSON data to the server and receive an excel file.
That excel file is created by the server and returned as a response to the client. Download that response as a file with custom name in browser"
$("#my-button").on("click", function(){
// Data to post
data = {
ids: [1, 2, 3, 4, 5]
};
// Use XMLHttpRequest instead of Jquery $ajax
xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
var a;
if (xhttp.readyState === 4 && xhttp.status === 200) {
// Trick for making downloadable link
a = document.createElement('a');
a.href = window.URL.createObjectURL(xhttp.response);
// Give filename you wish to download
a.download = "test-file.xls";
a.style.display = 'none';
document.body.appendChild(a);
a.click();
}
};
// Post data to URL which handles post request
xhttp.open("POST", excelDownloadUrl);
xhttp.setRequestHeader("Content-Type", "application/json");
// You should set responseType as blob for binary responses
xhttp.responseType = 'blob';
xhttp.send(JSON.stringify(data));
});
The above snippet is just doing following
Posting an array as JSON to the server using XMLHttpRequest.
After fetching content as a blob(binary), we are creating a downloadable URL and attaching it to invisible "a" link then clicking it.
Here we need to carefully set few things at the server side. I set few headers in Python Django HttpResponse. You need to set them accordingly if you use other programming languages.
# In python django code
response = HttpResponse(file_content, content_type="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
Since I download xls(excel) here, I adjusted contentType to above one. You need to set it according to your file type. You can use this technique to download any kind of files.

What server-side language are you using? In my app I can easily download a file from an AJAX call by setting the correct headers in PHP's response:
Setting headers server-side
header("HTTP/1.1 200 OK");
header("Pragma: public");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
// The optional second 'replace' parameter indicates whether the header
// should replace a previous similar header, or add a second header of
// the same type. By default it will replace, but if you pass in FALSE
// as the second argument you can force multiple headers of the same type.
header("Cache-Control: private", false);
header("Content-type: " . $mimeType);
// $strFileName is, of course, the filename of the file being downloaded.
// This won't have to be the same name as the actual file.
header("Content-Disposition: attachment; filename=\"{$strFileName}\"");
header("Content-Transfer-Encoding: binary");
header("Content-Length: " . mb_strlen($strFile));
// $strFile is a binary representation of the file that is being downloaded.
echo $strFile;
This will in fact 'redirect' the browser to this download page, but as #ahren alread said in his comment, it won't navigate away from the current page.
It's all about setting the correct headers so I'm sure you'll find a suitable solution for the server-side language you're using if it's not PHP.
Handling the response client side
Assuming you already know how to make an AJAX call, on the client side you execute an AJAX request to the server. The server then generates a link from where this file can be downloaded, e.g. the 'forward' URL where you want to point to.
For example, the server responds with:
{
status: 1, // ok
// unique one-time download token, not required of course
message: 'http://yourwebsite.com/getdownload/ska08912dsa'
}
When processing the response, you inject an iframe in your body and set the iframe's SRC to the URL you just received like this (using jQuery for the ease of this example):
$("body").append("<iframe src='" + data.message +
"' style='display: none;' ></iframe>");
If you've set the correct headers as shown above, the iframe will force a download dialog without navigating the browser away from the current page.
Note
Extra addition in relation to your question; I think it's best to always return JSON when requesting stuff with AJAX technology. After you've received the JSON response, you can then decide client-side what to do with it. Maybe, for example, later on you want the user to click a download link to the URL instead of forcing the download directly, in your current setup you would have to update both client and server-side to do so.

Here is how I got this working
https://stackoverflow.com/a/27563953/2845977
$.ajax({
url: '<URL_TO_FILE>',
success: function(data) {
var blob=new Blob([data]);
var link=document.createElement('a');
link.href=window.URL.createObjectURL(blob);
link.download="<FILENAME_TO_SAVE_WITH_EXTENSION>";
link.click();
}
});
Updated answer using download.js
$.ajax({
url: '<URL_TO_FILE>',
success: download.bind(true, "<FILENAME_TO_SAVE_WITH_EXTENSION>", "<FILE_MIME_TYPE>")
});

For those looking for a solution from an Angular perspective, this worked for me:
$http.post(
'url',
{},
{responseType: 'arraybuffer'}
).then(function (response) {
var headers = response.headers();
var blob = new Blob([response.data],{type:headers['content-type']});
var link = document.createElement('a');
link.href = window.URL.createObjectURL(blob);
link.download = "Filename";
link.click();
});

For those looking for a more modern approach, you can use the fetch API. The following code shows how to download a spreadsheet file.
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][1].
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.

I see you've already found out a solution, however I just wanted to add some information which may help someone trying to achieve the same thing with big POST requests.
I had the same issue a couple of weeks ago, indeed it isn't possible to achieve a "clean" download through AJAX, the Filament Group created a jQuery plugin which works exactly how you've already found out, it is called jQuery File Download however there is a downside to this technique.
If you're sending big requests through AJAX (say files +1MB) it will negatively impact responsiveness. In slow Internet connections you'll have to wait a lot until the request is sent and also wait for the file to download. It isn't like an instant "click" => "popup" => "download start". It's more like "click" => "wait until data is sent" => "wait for response" => "download start" which makes it appear the file double its size because you'll have to wait for the request to be sent through AJAX and get it back as a downloadable file.
If you're working with small file sizes <1MB you won't notice this. But as I discovered in my own app, for bigger file sizes it is almost unbearable.
My app allow users to export images dynamically generated, these images are sent through POST requests in base64 format to the server (it is the only possible way), then processed and sent back to users in form of .png, .jpg files, base64 strings for images +1MB are huge, this force users to wait more than necessary for the file to start downloading. In slow Internet connections it can be really annoying.
My solution for this was to temporary write the file to the server, once it is ready, dynamically generate a link to the file in form of a button which changes between "Please wait..." and "Download" states and at the same time, print the base64 image in a preview popup window so users can "right-click" and save it. This makes all the waiting time more bearable for users, and also speed things up.
Update Sep 30, 2014:
Months have passed since I posted this, finally I've found a better approach to speed things up when working with big base64 strings. I now store base64 strings into the database (using longtext or longblog fields), then I pass its record ID through the jQuery File Download, finally on the download script file I query the database using this ID to pull the base64 string and pass it through the download function.
Download Script Example:
<?php
// Record ID
$downloadID = (int)$_POST['id'];
// Query Data (this example uses CodeIgniter)
$data = $CI->MyQueries->GetDownload( $downloadID );
// base64 tags are replaced by [removed], so we strip them out
$base64 = base64_decode( preg_replace('#\[removed\]#', '', $data[0]->image) );
// This example is for base64 images
$imgsize = getimagesize( $base64 );
// Set content headers
header('Content-Disposition: attachment; filename="my-file.png"');
header('Content-type: '.$imgsize['mime']);
// Force download
echo $base64;
?>
I know this is way beyond what the OP asked, however I felt it would be good to update my answer with my findings. When I was searching for solutions to my problem, I read lots of "Download from AJAX POST data" threads which didn't give me the answer I was looking for, I hope this information helps someone looking to achieve something like this.

Here is my solution using a temporary hidden form.
//Create an hidden form
var form = $('<form>', {'method': 'POST', 'action': this.href}).hide();
//Add params
var params = { ...your params... };
$.each(params, function (k, v) {
form.append($('<input>', {'type': 'hidden', 'name': k, 'value': v}));
});
//Make it part of the document and submit
$('body').append(form);
form.submit();
//Clean up
form.remove();
Note that I massively use JQuery but you can do the same with native JS.

I want to point out some difficulties that arise when using the technique in the accepted answer, i.e. using a form post:
You can't set headers on the request. If your authentication schema involves headers, a Json-Web-Token passed in the Authorization header, you'll have to find other way to send it, for example as a query parameter.
You can't really tell when the request has finished. Well, you can use a cookie that gets set on response, as done by jquery.fileDownload, but it's FAR from perfect. It won't work for concurrent requests and it will break if a response never arrives.
If the server responds with a error, the user will be redirected to the error page.
You can only use the content types supported by a form. Which means you can't use JSON.
I ended up using the method of saving the file on S3 and sending a pre-signed URL to get the file.

As others have stated, you can create and submit a form to download via a POST request. However, you don't have to do this manually.
One really simple library for doing exactly this is jquery.redirect. It provides an API similar to the standard jQuery.post method:
$.redirect(url, [values, [method, [target]]])

This is a 3 years old question but I had the same problem today. I looked your edited solution but I think that it can sacrifice the performance because it has to make a double request. So if anyone needs another solution that doesn't imply to call the service twice then this is the way I did it:
<form id="export-csv-form" method="POST" action="/the/path/to/file">
<input type="hidden" name="anyValueToPassTheServer" value="">
</form>
This form is just used to call the service and avoid to use a window.location(). After that you just simply have to make a form submit from jquery in order to call the service and get the file. It's pretty simple but this way you can make a download using a POST. I now that this could be easier if the service you're calling is a GET, but that's not my case.

I used this FileSaver.js. In my case with csv files, i did this (in coffescript):
$.ajax
url: "url-to-server"
data: "data-to-send"
success: (csvData)->
blob = new Blob([csvData], { type: 'text/csv' })
saveAs(blob, "filename.csv")
I think for most complicated case, the data must be processed properly. Under the hood FileSaver.js implement the same approach of the answer of Jonathan Amend.

see: http://www.henryalgus.com/reading-binary-files-using-jquery-ajax/
it'll return a blob as a response, which can then be put into filesaver

Here is my solution, gathered from different sources:
Server side implementation :
String contentType = MediaType.APPLICATION_OCTET_STREAM_VALUE;
// Set headers
response.setHeader("content-disposition", "attachment; filename =" + fileName);
response.setContentType(contentType);
// Copy file to output stream
ServletOutputStream servletOutputStream = response.getOutputStream();
try (InputStream inputStream = new FileInputStream(file)) {
IOUtils.copy(inputStream, servletOutputStream);
} finally {
servletOutputStream.flush();
Utils.closeQuitely(servletOutputStream);
fileToDownload = null;
}
Client side implementation (using jquery):
$.ajax({
type: 'POST',
contentType: 'application/json',
url: <download file url>,
data: JSON.stringify(postObject),
error: function(XMLHttpRequest, textStatus, errorThrown) {
alert(errorThrown);
},
success: function(message, textStatus, response) {
var header = response.getResponseHeader('Content-Disposition');
var fileName = header.split("=")[1];
var blob = new Blob([message]);
var link = document.createElement('a');
link.href = window.URL.createObjectURL(blob);
link.download = fileName;
link.click();
}
});

Below is my solution for downloading multiple files depending on some list which consists of some ids and looking up in database, files will be determined and ready for download - if those exist.
I am calling C# MVC action for each file using Ajax.
And Yes, like others said, it is possible to do it in jQuery Ajax.
I did it with Ajax success and I am always sending response 200.
So, this is the key:
success: function (data, textStatus, xhr) {
And this is my code:
var i = 0;
var max = 0;
function DownloadMultipleFiles() {
if ($(".dataTables_scrollBody>tr.selected").length > 0) {
var list = [];
showPreloader();
$(".dataTables_scrollBody>tr.selected").each(function (e) {
var element = $(this);
var orderid = element.data("orderid");
var iscustom = element.data("iscustom");
var orderlineid = element.data("orderlineid");
var folderPath = "";
var fileName = "";
list.push({ orderId: orderid, isCustomOrderLine: iscustom, orderLineId: orderlineid, folderPath: folderPath, fileName: fileName });
});
i = 0;
max = list.length;
DownloadFile(list);
}
}
Then calling:
function DownloadFile(list) {
$.ajax({
url: '#Url.Action("OpenFile","OrderLines")',
type: "post",
data: list[i],
xhrFields: {
responseType: 'blob'
},
beforeSend: function (xhr) {
xhr.setRequestHeader("RequestVerificationToken",
$('input:hidden[name="__RequestVerificationToken"]').val());
},
success: function (data, textStatus, xhr) {
// check for a filename
var filename = "";
var disposition = xhr.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, '');
var a = document.createElement('a');
var url = window.URL.createObjectURL(data);
a.href = url;
a.download = filename;
document.body.append(a);
a.click();
a.remove();
window.URL.revokeObjectURL(url);
}
else {
getErrorToastMessage("Production file for order line " + list[i].orderLineId + " does not exist");
}
i = i + 1;
if (i < max) {
DownloadFile(list);
}
},
error: function (XMLHttpRequest, textStatus, errorThrown) {
},
complete: function () {
if(i===max)
hidePreloader();
}
});
}
C# MVC:
[HttpPost]
[ValidateAntiForgeryToken]
public IActionResult OpenFile(OrderLineSimpleModel model)
{
byte[] file = null;
try
{
if (model != null)
{
//code for getting file from api - part is missing here as not important for this example
file = apiHandler.Get<byte[]>(downloadApiUrl, token);
var contentDispositionHeader = new System.Net.Mime.ContentDisposition
{
Inline = true,
FileName = fileName
};
// Response.Headers.Add("Content-Disposition", contentDispositionHeader.ToString() + "; attachment");
Response.Headers.Add("Content-Type", "application/pdf");
Response.Headers.Add("Content-Disposition", "attachment; filename=" + fileName);
Response.Headers.Add("Content-Transfer-Encoding", "binary");
Response.Headers.Add("Content-Length", file.Length.ToString());
}
}
catch (Exception ex)
{
this.logger.LogError(ex, "Error getting pdf", null);
return Ok();
}
return File(file, System.Net.Mime.MediaTypeNames.Application.Pdf);
}
As long as you return response 200, success in Ajax can work with it, you can check if file actually exist or not as the line below in this case would be false and you can inform user about that:
if (disposition && disposition.indexOf('attachment') !== -1) {

To get Jonathan Amends answer to work in Edge I made the following changes:
var blob = typeof File === 'function'
? new File([this.response], filename, { type: type })
: new Blob([this.response], { type: type });
to this
var f = typeof File+"";
var blob = f === 'function' && Modernizr.fileapi
? new File([this.response], filename, { type: type })
: new Blob([this.response], { type: type });
I would rather have posted this as a comment but I don't have enough reputation for that

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.

If response is an Array Buffer, try this under onsuccess event in Ajax:
if (event.data instanceof ArrayBuffer) {
var binary = '';
var bytes = new Uint8Array(event.data);
for (var i = 0; i < bytes.byteLength; i++) {
binary += String.fromCharCode(bytes[i])
}
$("#some_id").append("<li><img src=\"data:image/png;base64," + window.btoa(binary) + "\"/></span></li>");
return;
}
where event.data is response received in success function of xhr event.

I needed a similar solution to #alain-cruz's one, but in nuxt/vue with multiple downloads. I know browsers block multiple file downloads, and I also have API which returns a set of csv formatted data.I was going to use JSZip at first but I needed IE support so here is my solution. If anyone can help me improve this that would be great, but it's working for me so far.
API returns:
data : {
body: {
fileOne: ""col1", "col2", "datarow1.1", "datarow1.2"...so on",
fileTwo: ""col1", "col2"..."
}
}
page.vue:
<template>
<b-link #click.prevent="handleFileExport">Export<b-link>
</template>
export default = {
data() {
return {
fileNames: ['fileOne', 'fileTwo'],
}
},
computed: {
...mapState({
fileOne: (state) => state.exportFile.fileOne,
fileTwo: (state) => state.exportFile.fileTwo,
}),
},
method: {
handleExport() {
//exportFileAction in store/exportFile needs to return promise
this.$store.dispatch('exportFile/exportFileAction', paramsToSend)
.then(async (response) => {
const downloadPrep = this.fileNames.map(async (fileName) => {
// using lodash to get computed data by the file name
const currentData = await _.get(this, `${fileName}`);
const currentFileName = fileName;
return { currentData, currentFileName };
});
const response = await Promise.all(downloadPrep);
return response;
})
.then(async (data) => {
data.forEach(({ currentData, currentFileName }) => {
this.forceFileDownload(currentData, currentFileName);
});
})
.catch(console.error);
},
forceFileDownload(data, fileName) {
const url = window.URL
.createObjectURL(new Blob([data], { type: 'text/csv;charset=utf-8;' }));
const link = document.createElement('a');
link.href = url;
link.setAttribute('download', `${fileName}.csv`);
document.body.appendChild(link);
link.click();
},
}

I used Naren Yellavula's solution and got it working with few changes to the script, after trying several other solutions using jquery. But, jquery will not download a zip file properly. I can't unzip the file after download.
In my use case, I have to upload a zip file, which is unzipped in the Servlet, files are processed and zipped again before the zip file is downloaded to the client. This is what you need to do on client side.
$('#fileUpBtn').click(function (e){
e.preventDefault();
var file = $('#fileUpload')[0].files[0];
var formdata = new FormData();
formdata.append('file', file);
// Use XMLHttpRequest instead of Jquery $ajax to download zip files
xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (xhttp.readyState === 4 && xhttp.status === 200) {
var a = document.createElement('a');
a.href = window.URL.createObjectURL(xhttp.response);
a.download = "modified_" + file.name;
a.style.display = 'none';
document.body.appendChild(a);
a.click();
document.body.removeChild(a);
window.URL.revokeObjectURL(a.href);
}
};
xhttp.open("POST", "<URL to Servlet>", true);
xhttp.responseType = 'blob';
xhttp.send(formdata);
});
<div class="form-group">
<label id="fileUpLabel" for="fileUpload"></label>
<input type="file" class="form-control" id="fileUpload" name="file" accept="" required/>
</div>
<button class="btn" type="submit" id="fileUpBtn"></button>

How can I send a binary data (blob) using fetch and FormData?

The following code works as expected. Open the page "https://wiki.epfl.ch/" on Google Chrome, and execute this code on the Developer console. Note: the page "https://wiki.epfl.ch/test.php" does not exists and so it fails to load, but that's not the issue.
response = await fetch("https://wiki.epfl.ch/lapa-studio/documents/DTS/laser%20tutorial.pdf");
response.text().then(function(content) {
formData = new FormData();
console.log(content.length);
console.log(content);
formData.append("content", content);
fetch("https://wiki.epfl.ch/test.php", {method: 'POST', body: formData});
})
It logs:
content.length: 57234
content: %PDF-1.3
%���������
4 0 obj
<< /Length 5 0 R /Filter /FlateDecode >>
stream
x��K��F�����;¢�
...
Go to the Developer Network tab, choose the 'test.php' page, navigate to "Requested payload:" and you can see this content:
------WebKitFormBoundaryOJOOGb7N43BxCRlv
Content-Disposition: form-data; name="content"
%PDF-1.3
%���������
4 0 obj
<< /Length 5 0 R /Filter /FlateDecode >>
stream
...
------WebKitFormBoundaryOJOOGb7N43BxCRlv
The issue is that the request file is a binary file (PDF), and the text gets "mangled". It reports a size of 57234 bytes, when the actual file size (as fetched with a wget command) is 60248 bytes.
The question is: How to get and send the binary data, without being modified?
I tried replacing response.text() by response.blob(), as follows:
response = await fetch("https://wiki.epfl.ch/lapa-studio/documents/DTS/laser%20tutorial.pdf");
response.blob().then(function(content) {
console.log(content.size);
console.log(content);
formData = new FormData();
formData.append("content", content);
fetch("https://wiki.epfl.ch/test.php", {method: 'POST', body: formData});
})
Now I get this log, with the correct file size:
content.size: 60248
content: Blob(60248) {size: 60248, type: "application/pdf"}
However, going to the Developer Network tab, choose the 'test.php' page, navigate to "Requested payload:", it shows that it sends an empty payload:
------WebKitFormBoundaryYoibuD14Ah2cNGAd
Content-Disposition: form-data; name="content"; filename="blob"
Content-Type: application/pdf
------WebKitFormBoundaryYoibuD14Ah2cNGAd--
Note: The webpage I am developing is not at wiki.epfl.ch. I provide this example so that users can try it (and avoid the "Cross-Origin Resource Sharing" problem). My "test.php" page is in php and $_POST['content'] returns the content when using response.text(), but it returns empty when using response.blob(). So, even if it is the case that the Developer Network tab "Requested payload:" does not show binary data, this snipped is still not working.

If you want to send a binary file, do not use the .text() method, as that returns the file decoded using UTF-8, which is not what you want. Instead, use the .blob() method, which does not attempt to decode the file, and use it directly as the body parameter of the second fetch() since it's allowed to be a Blob:
const response = await fetch("https://wiki.epfl.ch/lapa-studio/documents/DTS/laser%20tutorial.pdf");
const content = await response.blob();
console.log(content.size);
fetch("https://wiki.epfl.ch/test.php", { method: 'POST', body: content });
For parsing this upload format see this answer.
If you want to upload it as part of a multipart/form-data formatted attachment, you can still use the FormData API, but doing so isn't necessary to send the binary data to your PHP script. Just for completeness, here's how you'd do that instead:
const response = await fetch("https://wiki.epfl.ch/lapa-studio/documents/DTS/laser%20tutorial.pdf");
const content = await response.blob();
console.log(content.size);
const formData = new FormData();
formData.append("content", content);
fetch("https://wiki.epfl.ch/test.php", { method: 'POST', body: formData });

Try this, by converting blob to DataURL string, you can send binary data without being modified.
response = await fetch("https://wiki.epfl.ch/lapa-studio/documents/DTS/laser%20tutorial.pdf");
response.blob().then(function (content) {
let reader = new FileReader();
reader.addEventListener("loadend", function () {
formData = new FormData();
formData.append("content", reader.result);
fetch("https://wiki.epfl.ch/test.php", { method: 'POST', body: formData });
reader.removeEventListener("loadend");
});
reader.readAsDataURL(content);
});

Please Try with this code may hope it will helps you
pdfcall(){
var xmlhttp = new XMLHttpRequest(),
method = 'GET',
xmlhttp.open(method, url, true);
xmlhttp.responseType = 'blob';
xmlhttp.onload = (e: any) => {
console.log(xmlhttp);
if (xmlhttp.status === 200) {
let blob = new Blob([xmlhttp.response], {type: 'application/pdf'});
this.pdfSrc = URL.createObjectURL(blob);
}
};
xmlhttp.onerror = (e: any) =>{
console.error(e,'eerr')
}
xmlhttp.send();
}

Direct uploading to AWS S3 : SignatureDoesNotMatch only for IE

I use Amazon Web Service S3 to upload and store my files. I generate a pre signed url with AWS Sdk for Node.js server-side to upload directly files from browser thanks to this pre signed url.
How it works
Server-side I have a method wich returns the pre-signed url.
AWS.config.loadFromPath(__dirname + '/../properties/aws-config.json');
AWS.config.region = 'eu-west-1';
//Credentials are loaded
var s3 = new AWS.S3();
var docId = req.query.doc;
var params = {
Bucket: res.locals.user.bucketId,
Key: docId+"."+req.query.fileExtension,
ACL : "bucket-owner-read",
ContentType : req.query.fileType
};
s3.getSignedUrl('putObject', params, function (err, url) {
if(url){
res.writeHead(200);
var result = {
AWSUrl : url
};
//Generates pre signed URL with signature param
res.end(JSON.stringify(result));
}
}
I upload directly my file to S3 client-side
var loadToAWSS3 = function(url, file, inputFileId){
var data = new FormData();
data.append('file', file);
$.ajax({
url: url,//url getted from server-side method
type: 'PUT',
data : data,
headers: {
'Content-Type': file.type
},
processData: false,
xhr: function() {
var myXhr = $.ajaxSettings.xhr();
if(myXhr.upload){
myXhr.upload.addEventListener('progress',function(e){
if(e.lengthComputable){
var max = e.total;
var current = e.loaded;
var percentage = (current * 100)/max;
//stuff to handle progress...
}
},
false);
}
return myXhr;
},
statusCode: {
200: function () {
//some stuff
}
});
}
Chrome & Firefox behaviors
Works as expected, the pre signed url is getted, then the file is uploaded, I can see it in my AWS S3 console.
Lovely IE 11
SignatureDoesNotMatch error ! IE add some extra stuff to Content-Type request header not expected by AWS which causes error in the signature comparison. Server-side, the Sdk generates signature based on :
ContentType : req.query.fileType //(something like application/pdf)
whereas when I inspect the request with IE debugger, I see
Content-Type application/pdf, multipart/form-data; boundary=---------------------------7df2f3283091c
in Chrome my request header is fine
Content-Type: application/pdf
What can I do to remove this IE extra Content-Type ? If not possible, how can I generate this extra stuff before sending the request in order to get the pre-signed url with the extra stuff in the signature ?

OK, I finally figured it out.
Using FormData() simulates that you are sending files through a form. That's why IE always adds
multipart/form-data; boundary=---------------------------7**********
To get around the problem I use raw Javascript with XMLHttpRequest thanks to this answer
var xmlHttpRequest = new XMLHttpRequest();
xmlHttpRequest.open('PUT', url, true);
xmlHttpRequest.setRequestHeader('Content-Type', file.type);
xmlHttpRequest.send(file);
And it works with Chrome, Firefox, IE 11 (I have not tested with IE<11 but according to W3Schools it works for IE7+). No more extra content type with IE.
Hope this helps

if you have access to xhr you can do:
var _send = xhr.send;
xhr.send = function() {
_send.call(xhr, file);
}