Develop Reference

Download string data as file based on the file type (text/Json)

I am trying to downloading a string data as file such as text, and json files based on the fileType we are passing as parameter. I have tried below code.
function downloadString(text, fileType, fileName) {
var blob = new Blob([text], { type: fileType });
var a = document.createElement('a');
a.download = fileName;
a.href = URL.createObjectURL(blob);
a.dataset.downloadurl = [fileType, a.download, a.href].join(':');
a.style.display = "none";
document.body.appendChild(a);
a.click();
document.body.removeChild(a);
setTimeout(function() { URL.revokeObjectURL(a.href); }, 1500);
}
Downloading is working. But it always download txt file even if we pass json filetype.
Can anyone help this?

Using javascript Blob to save data as a CSS file

I have the following function to save a file to the browser using blob...
var saveData = (function () {
var a = document.createElement("a");
document.body.appendChild(a);
a.style = "display: none";
return function (data, fileName) {
var json = JSON.stringify(data),
blob = new Blob([json], {type: "octet/stream"}),
url = window.URL.createObjectURL(blob);
a.href = url;
a.download = fileName;
a.click();
window.URL.revokeObjectURL(url);
};
}());
I am passing the following data to it...
var filename = "style.css";
var data = CSSFile //CSS string
saveData(data, filename)
My data is a string of CSS attributes that I want to save as a CSS file. The problem is, when I open the downloaded CSS file, it look like...
"html, body {....} ... "
Notice it is surrounded by double quotes. I need these removed. I tried the following...
CSSFile = CSSFile.substring(0, CSSFile.length - 1);
saveData(data, filename)
But all that did was remove the first character inside the double quotes...
"tml,body{...}..."
How can I save the string without the double quotes?

You are getting quotes in your string because you are running it through JSON.stringify when it is already a string.
Try this instead.
var saveData = (function () {
var a = document.createElement("a");
document.body.appendChild(a);
a.style = "display: none";
return function (data, fileName) {
var blob = new Blob([data], {type: "octet/stream"}),
url = window.URL.createObjectURL(blob);
a.href = url;
a.download = fileName;
a.click();
window.URL.revokeObjectURL(url);
};
}());

PDF is blank when downloading using javascript

I have a web service that returns PDF file content in its response. I want to download this as a pdf file when user clicks the link. The javascript code that I have written in UI is as follows:
$http.get('http://MyPdfFileAPIstreamURl').then(function(response){
var blob=new File([response],'myBill.pdf',{type: "text/pdf"});
var link=document.createElement('a');
link.href=window.URL.createObjectURL(blob);
link.download="myBill.pdf";
link.click();
});
'response' contains the PDF byte array from servlet outputstream of 'MyPdfFileAPIstreamURl'. And also the stream is not encrypted.
So when I click the link, a PDF file gets downloaded successfully of size around 200KB. But when I open this file, it opens up with blank pages. The starting content of the downloaded pdf file is in the image.
I can't understand what is wrong here. Help !
This is the downloaded pdf file starting contents:

solved it via XMLHttpRequest and xhr.responseType = 'arraybuffer';
code:
var xhr = new XMLHttpRequest();
xhr.open('GET', './api/exportdoc/report_'+id, true);
xhr.responseType = 'arraybuffer';
xhr.onload = function(e) {
if (this.status == 200) {
var blob=new Blob([this.response], {type:"application/pdf"});
var link=document.createElement('a');
link.href=window.URL.createObjectURL(blob);
link.download="Report_"+new Date()+".pdf";
link.click();
}
};
xhr.send();

i fetched the data from server as string(which is base64 encoded to string) and then on client side i decoded it to base64 and then to array buffer.
Sample code
function solution1(base64Data) {
var arrBuffer = base64ToArrayBuffer(base64Data);
// It is necessary to create a new blob object with mime-type explicitly set
// otherwise only Chrome works like it should
var newBlob = new Blob([arrBuffer], { type: "application/pdf" });
// IE doesn't allow using a blob object directly as link href
// instead it is necessary to use msSaveOrOpenBlob
if (window.navigator && window.navigator.msSaveOrOpenBlob) {
window.navigator.msSaveOrOpenBlob(newBlob);
return;
}
// For other browsers:
// Create a link pointing to the ObjectURL containing the blob.
var data = window.URL.createObjectURL(newBlob);
var link = document.createElement('a');
document.body.appendChild(link); //required in FF, optional for Chrome
link.href = data;
link.download = "file.pdf";
link.click();
window.URL.revokeObjectURL(data);
link.remove();
}
function base64ToArrayBuffer(data) {
var binaryString = window.atob(data);
var binaryLen = binaryString.length;
var bytes = new Uint8Array(binaryLen);
for (var i = 0; i < binaryLen; i++) {
var ascii = binaryString.charCodeAt(i);
bytes[i] = ascii;
}
return bytes;
};

I was facing the same problem in my React project.
On the API I was using res.download() of express to attach the PDF file in the response. By doing that, I was receiving a string based file. That was the real reason why the file was opening blank or corrupted.
In my case the solution was to force the responseType to 'blob'. Since I was making the request via axios, I just simply added this attr in the option object:
axios.get('your_api_url_here', { responseType: 'blob' })
After, to make the download happen, you can do something like this in your 'fetchFile' method:
const response = await youtServiceHere.fetchFile(id)
const pdfBlob = new Blob([response.data], { type: "application/pdf" })
const blobUrl = window.URL.createObjectURL(pdfBlob)
const link = document.createElement('a')
link.href = blobUrl
link.setAttribute('download', customNameIfYouWantHere)
link.click();
link.remove();
URL.revokeObjectURL(blobUrl);

solved it thanks to rom5jp but adding the sample code for golang and nextjs
in golang using with gingonic context
c.Header("Content-Description", "File-Transfer")
c.Header("Content-Transfer-Encoding", "binary")
c.Header("Content-Disposition","attachment; filename="+fileName)
c.Header("Content-Type", "application/pdf; charset=utf-8")
c.File(targetPath)
//c.FileAttachment(targetPath,fileName)
os.RemoveAll(targetPath)
in next js
const convertToPDF = (res) => {
const uuid = generateUUID();
var a = document.createElement('a');
var url = window.URL.createObjectURL(new Blob([res],{type: "application/pdf"}));
a.href = url;
a.download = 'report.pdf';
a.click();
window.URL.revokeObjectURL(url);
}
const convertFile = async() => {
axios.post('http://localhost:80/fileconverter/upload', {
"token_id" : cookies.access_token,
"request_type" : 1,
"url" : url
},{
responseType: 'blob'
}).then((res)=>{
convertToPDF(res.data)
}, (err) => {
console.log(err)
})
}

I was able to get this working with fetch using response.blob()
fetch(url)
.then((response) => response.blob())
.then((response) => {
const blob = new Blob([response], {type: 'application/pdf'});
const link = document.createElement('a');
link.download = 'some.pdf';
link.href = URL.createObjectURL(blob);
link.click();
});

Changing the request from POST to GET fixed it for me

File download a byte array as a file in javascript / Extjs

In my Ext Js solution I am calling a service which is returning this JSON format
{"success":true,"filename":"spreadsheet.xlsx","file":[80,75,3,4,20,0,...(many more)]}
How can I make a file download dialog with the filename and the content of the byte array (file) ?
UPDATE
So I found this bit to start the downlaod
var a = window.document.createElement('a');
a.href = window.URL.createObjectURL(new Blob(data.file, { type: 'application/octet-stream' }));
a.download = data.filename;
// Append anchor to body.
document.body.appendChild(a)
a.click();
// Remove anchor from body
document.body.removeChild(a)
So far good
But the file I get is corrupted so I suspect I need to Encode/Decode the file variable?

I had to convert the file into a Uint8Array before passing it to the Blob
var arr = data.file;
var byteArray = new Uint8Array(arr);
var a = window.document.createElement('a');
a.href = window.URL.createObjectURL(new Blob([byteArray], { type: 'application/octet-stream' }));
a.download = data.filename;
// Append anchor to body.
document.body.appendChild(a)
a.click();
// Remove anchor from body
document.body.removeChild(a)
Reading this answer helped a lot https://stackoverflow.com/a/16245768/1016439

Building on Jepzen's response, I was able to use this technique to download a document from AWS S3 from within the browser. +1 Jepzen
s3.getObject(params, function(err, data) {
if (err === null) {
var arr = data.Body;
var byteArray = new Uint8Array(arr);
var a = window.document.createElement('a');
a.href = window.URL.createObjectURL(new Blob([byteArray], { type: 'application/octet-stream' }));
a.download = fName; //fName was the file name portion of the key what was passed in as part of the key value within params.
// Append anchor to body.
document.body.appendChild(a)
a.click();
// Remove anchor from body
document.body.removeChild(a)
} else {
result = 'failure'
console.log("Failed to retrieve an object: " + err);
}
});

Saving a Uint8Array to a binary file

I am working on a web app that opens binary files and allows them to be edited.
This process is basically ondrop -> dataTransfer.files[0] -> FileReader -> Uint8Array
Essentially, I want to be able to save the modified file back as a binary file. Ideally as a file download with a specified file name.
There doesn't seem to be any standard method of doing this, and that sucks, because everything up to that point is well supported.
I am currently converting the array to a string using String.fromCharCode(), base64 encoding that, and using a data uri in a hyperlink like data:application/octet-stream;base64,.., along with the download attribute to specify filename.
It seems to work, but it's quite hacky and I think converting the raw bytes to a string might introduce encoding issues depending on the byte values. I don't want the data to become corrupt or break the string.
Barring that, is there a better/proper method for getting an array of bytes as a binary file to the user?

These are utilities that I use to download files cross-browser. The nifty thing about this is that you can actually set the download property of a link to the name you want your filename to be.
FYI the mimeType for binary is application/octet-stream
var downloadBlob, downloadURL;
downloadBlob = function(data, fileName, mimeType) {
var blob, url;
blob = new Blob([data], {
type: mimeType
});
url = window.URL.createObjectURL(blob);
downloadURL(url, fileName);
setTimeout(function() {
return window.URL.revokeObjectURL(url);
}, 1000);
};
downloadURL = function(data, fileName) {
var a;
a = document.createElement('a');
a.href = data;
a.download = fileName;
document.body.appendChild(a);
a.style = 'display: none';
a.click();
a.remove();
};
Usage:
downloadBlob(myBinaryBlob, 'some-file.bin', 'application/octet-stream');

(shorter) ES6 version of the top answer:
const downloadURL = (data, fileName) => {
const a = document.createElement('a')
a.href = data
a.download = fileName
document.body.appendChild(a)
a.style.display = 'none'
a.click()
a.remove()
}
const downloadBlob = (data, fileName, mimeType) => {
const blob = new Blob([data], {
type: mimeType
})
const url = window.URL.createObjectURL(blob)
downloadURL(url, fileName)
setTimeout(() => window.URL.revokeObjectURL(url), 1000)
}