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I have base64 stream of a pdf file. Now I need to convert it into a pdf file in Native Javascript. How can I do that? [duplicate]

I have Base64-encoded binary data in a string:
const contentType = 'image/png';
const b64Data = 'iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==';
I would like to create a blob: URL containing this data and display it to the user:
const blob = new Blob(????, {type: contentType});
const blobUrl = URL.createObjectURL(blob);
window.location = blobUrl;
I haven't been been able to figure out how to create the BLOB.
In some cases I am able to avoid this by using a data: URL instead:
const dataUrl = `data:${contentType};base64,${b64Data}`;
window.location = dataUrl;
However, in most cases the data: URLs are prohibitively large.
How can I decode a Base64 string to a BLOB object in JavaScript?

The atob function will decode a Base64-encoded string into a new string with a character for each byte of the binary data.
const byteCharacters = atob(b64Data);
Each character's code point (charCode) will be the value of the byte. We can create an array of byte values by applying this using the .charCodeAt method for each character in the string.
const byteNumbers = new Array(byteCharacters.length);
for (let i = 0; i < byteCharacters.length; i++) {
byteNumbers[i] = byteCharacters.charCodeAt(i);
}
You can convert this array of byte values into a real typed byte array by passing it to the Uint8Array constructor.
const byteArray = new Uint8Array(byteNumbers);
This in turn can be converted to a BLOB by wrapping it in an array and passing it to the Blob constructor.
const blob = new Blob([byteArray], {type: contentType});
The code above works. However the performance can be improved a little by processing the byteCharacters in smaller slices, rather than all at once. In my rough testing 512 bytes seems to be a good slice size. This gives us the following function.
const b64toBlob = (b64Data, contentType='', sliceSize=512) => {
const byteCharacters = atob(b64Data);
const byteArrays = [];
for (let offset = 0; offset < byteCharacters.length; offset += sliceSize) {
const slice = byteCharacters.slice(offset, offset + sliceSize);
const byteNumbers = new Array(slice.length);
for (let i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
const byteArray = new Uint8Array(byteNumbers);
byteArrays.push(byteArray);
}
const blob = new Blob(byteArrays, {type: contentType});
return blob;
}
const blob = b64toBlob(b64Data, contentType);
const blobUrl = URL.createObjectURL(blob);
window.location = blobUrl;
Full Example:
const b64toBlob = (b64Data, contentType='', sliceSize=512) => {
const byteCharacters = atob(b64Data);
const byteArrays = [];
for (let offset = 0; offset < byteCharacters.length; offset += sliceSize) {
const slice = byteCharacters.slice(offset, offset + sliceSize);
const byteNumbers = new Array(slice.length);
for (let i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
const byteArray = new Uint8Array(byteNumbers);
byteArrays.push(byteArray);
}
const blob = new Blob(byteArrays, {type: contentType});
return blob;
}
const contentType = 'image/png';
const b64Data = 'iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==';
const blob = b64toBlob(b64Data, contentType);
const blobUrl = URL.createObjectURL(blob);
const img = document.createElement('img');
img.src = blobUrl;
document.body.appendChild(img);

Here is a more minimal method without any dependencies or libraries.
It requires the new fetch API. (Can I use it?)
var url = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg=="
fetch(url)
.then(res => res.blob())
.then(console.log)
With this method you can also easily get a ReadableStream, ArrayBuffer, text, and JSON.
(fyi this also works with node-fetch in Node)
As a function:
const b64toBlob = (base64, type = 'application/octet-stream') =>
fetch(`data:${type};base64,${base64}`).then(res => res.blob())
But I would encourage you to don't use base64 in the first place. There are better ways to send and receive binary data. JSON isn't always the best option. it takes up more bandwidth and waste processing time (de)encodeing stuff. Us eg canvas.toBlob instead of canvas.toDataURL and use FormData to send binary files. you can also return back a multipart payload and decode it using await response.formData() that is coming from a server response. FormData can go both ways.
I did a simple performance test towards Jeremy's ES6 sync version.
The sync version will block UI for a while.
keeping the devtool open can slow the fetch performance
document.body.innerHTML += '<input autofocus placeholder="try writing">'
// get some dummy gradient image
var img=function(){var a=document.createElement("canvas"),b=a.getContext("2d"),c=b.createLinearGradient(0,0,1500,1500);a.width=a.height=3000;c.addColorStop(0,"red");c.addColorStop(1,"blue");b.fillStyle=c;b.fillRect(0,0,a.width,a.height);return a.toDataURL()}();
async function perf() {
const blob = await fetch(img).then(res => res.blob())
// turn it to a dataURI
const url = img
const b64Data = url.split(',')[1]
// Jeremy Banks solution
const b64toBlob = (b64Data, contentType = '', sliceSize=512) => {
const byteCharacters = atob(b64Data);
const byteArrays = [];
for (let offset = 0; offset < byteCharacters.length; offset += sliceSize) {
const slice = byteCharacters.slice(offset, offset + sliceSize);
const byteNumbers = new Array(slice.length);
for (let i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
const byteArray = new Uint8Array(byteNumbers);
byteArrays.push(byteArray);
}
const blob = new Blob(byteArrays, {type: contentType});
return blob;
}
// bench blocking method
let i = 500
console.time('blocking b64')
while (i--) {
await b64toBlob(b64Data)
}
console.timeEnd('blocking b64')
// bench non blocking
i = 500
// so that the function is not reconstructed each time
const toBlob = res => res.blob()
console.time('fetch')
while (i--) {
await fetch(url).then(toBlob)
}
console.timeEnd('fetch')
console.log('done')
}
perf()

Optimized (but less readable) implementation:
function base64toBlob(base64Data, contentType) {
contentType = contentType || '';
var sliceSize = 1024;
var byteCharacters = atob(base64Data);
var bytesLength = byteCharacters.length;
var slicesCount = Math.ceil(bytesLength / sliceSize);
var byteArrays = new Array(slicesCount);
for (var sliceIndex = 0; sliceIndex < slicesCount; ++sliceIndex) {
var begin = sliceIndex * sliceSize;
var end = Math.min(begin + sliceSize, bytesLength);
var bytes = new Array(end - begin);
for (var offset = begin, i = 0; offset < end; ++i, ++offset) {
bytes[i] = byteCharacters[offset].charCodeAt(0);
}
byteArrays[sliceIndex] = new Uint8Array(bytes);
}
return new Blob(byteArrays, { type: contentType });
}

Following is my TypeScript code which can be converted easily into JavaScript and you can use
/**
* Convert BASE64 to BLOB
* #param base64Image Pass Base64 image data to convert into the BLOB
*/
private convertBase64ToBlob(base64Image: string) {
// Split into two parts
const parts = base64Image.split(';base64,');
// Hold the content type
const imageType = parts[0].split(':')[1];
// Decode Base64 string
const decodedData = window.atob(parts[1]);
// Create UNIT8ARRAY of size same as row data length
const uInt8Array = new Uint8Array(decodedData.length);
// Insert all character code into uInt8Array
for (let i = 0; i < decodedData.length; ++i) {
uInt8Array[i] = decodedData.charCodeAt(i);
}
// Return BLOB image after conversion
return new Blob([uInt8Array], { type: imageType });
}

See this example: https://jsfiddle.net/pqhdce2L/
function b64toBlob(b64Data, contentType, sliceSize) {
contentType = contentType || '';
sliceSize = sliceSize || 512;
var byteCharacters = atob(b64Data);
var byteArrays = [];
for (var offset = 0; offset < byteCharacters.length; offset += sliceSize) {
var slice = byteCharacters.slice(offset, offset + sliceSize);
var byteNumbers = new Array(slice.length);
for (var i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
var byteArray = new Uint8Array(byteNumbers);
byteArrays.push(byteArray);
}
var blob = new Blob(byteArrays, {type: contentType});
return blob;
}
var contentType = 'image/png';
var b64Data = Your Base64 encode;
var blob = b64toBlob(b64Data, contentType);
var blobUrl = URL.createObjectURL(blob);
var img = document.createElement('img');
img.src = blobUrl;
document.body.appendChild(img);

For all browser support, especially on Android, perhaps you can add this:
try{
blob = new Blob(byteArrays, {type : contentType});
}
catch(e){
// TypeError old Google Chrome and Firefox
window.BlobBuilder = window.BlobBuilder ||
window.WebKitBlobBuilder ||
window.MozBlobBuilder ||
window.MSBlobBuilder;
if(e.name == 'TypeError' && window.BlobBuilder){
var bb = new BlobBuilder();
bb.append(byteArrays);
blob = bb.getBlob(contentType);
}
else if(e.name == "InvalidStateError"){
// InvalidStateError (tested on FF13 WinXP)
blob = new Blob(byteArrays, {type : contentType});
}
else{
// We're screwed, blob constructor unsupported entirely
}
}

For all copy-paste lovers out there like me, here is a cooked download function which works on Chrome, Firefox and Edge:
window.saveFile = function (bytesBase64, mimeType, fileName) {
var fileUrl = "data:" + mimeType + ";base64," + bytesBase64;
fetch(fileUrl)
.then(response => response.blob())
.then(blob => {
var link = window.document.createElement("a");
link.href = window.URL.createObjectURL(blob, { type: mimeType });
link.download = fileName;
document.body.appendChild(link);
link.click();
document.body.removeChild(link);
});
}

I'm posting a more declarative way of sync Base64 converting. While async fetch().blob() is very neat and I like this solution a lot, it doesn't work on Internet Explorer 11 (and probably Edge - I haven't tested this one), even with the polyfill - take a look at my comment to Endless' post for more details.
const blobPdfFromBase64String = base64String => {
const byteArray = Uint8Array.from(
atob(base64String)
.split('')
.map(char => char.charCodeAt(0))
);
return new Blob([byteArray], { type: 'application/pdf' });
};
Bonus
If you want to print it you could do something like:
const isIE11 = !!(window.navigator && window.navigator.msSaveOrOpenBlob); // Or however you want to check it
const printPDF = blob => {
try {
isIE11
? window.navigator.msSaveOrOpenBlob(blob, 'documents.pdf')
: printJS(URL.createObjectURL(blob)); // http://printjs.crabbly.com/
} catch (e) {
throw PDFError;
}
};
Bonus x 2 - Opening a BLOB file in new tab for Internet Explorer 11
If you're able to do some preprocessing of the Base64 string on the server you could expose it under some URL and use the link in printJS :)

For image data, I find it simpler to use canvas.toBlob (asynchronous)
function b64toBlob(b64, onsuccess, onerror) {
var img = new Image();
img.onerror = onerror;
img.onload = function onload() {
var canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
var ctx = canvas.getContext('2d');
ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
canvas.toBlob(onsuccess);
};
img.src = b64;
}
var base64Data = 'data:image/jpg;base64,/9j/4AAQSkZJRgABAQA...';
b64toBlob(base64Data,
function(blob) {
var url = window.URL.createObjectURL(blob);
// do something with url
}, function(error) {
// handle error
});

If you can stand adding one dependency to your project there's the great blob-util npm package that provides a handy base64StringToBlob function. Once added to your package.json you can use it like this:
import { base64StringToBlob } from 'blob-util';
const contentType = 'image/png';
const b64Data = 'iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==';
const blob = base64StringToBlob(b64Data, contentType);
// Do whatever you need with your blob...

I noticed that Internet Explorer 11 gets incredibly slow when slicing the data like Jeremy suggested. This is true for Chrome, but Internet Explorer seems to have a problem when passing the sliced data to the Blob-Constructor. On my machine, passing 5 MB of data makes Internet Explorer crash and memory consumption is going through the roof. Chrome creates the blob in no time.
Run this code for a comparison:
var byteArrays = [],
megaBytes = 2,
byteArray = new Uint8Array(megaBytes*1024*1024),
block,
blobSlowOnIE, blobFastOnIE,
i;
for (i = 0; i < (megaBytes*1024); i++) {
block = new Uint8Array(1024);
byteArrays.push(block);
}
//debugger;
console.profile("No Slices");
blobSlowOnIE = new Blob(byteArrays, { type: 'text/plain'});
console.profileEnd();
console.profile("Slices");
blobFastOnIE = new Blob([byteArray], { type: 'text/plain'});
console.profileEnd();
So I decided to include both methods described by Jeremy in one function. Credits go to him for this.
function base64toBlob(base64Data, contentType, sliceSize) {
var byteCharacters,
byteArray,
byteNumbers,
blobData,
blob;
contentType = contentType || '';
byteCharacters = atob(base64Data);
// Get BLOB data sliced or not
blobData = sliceSize ? getBlobDataSliced() : getBlobDataAtOnce();
blob = new Blob(blobData, { type: contentType });
return blob;
/*
* Get BLOB data in one slice.
* => Fast in Internet Explorer on new Blob(...)
*/
function getBlobDataAtOnce() {
byteNumbers = new Array(byteCharacters.length);
for (var i = 0; i < byteCharacters.length; i++) {
byteNumbers[i] = byteCharacters.charCodeAt(i);
}
byteArray = new Uint8Array(byteNumbers);
return [byteArray];
}
/*
* Get BLOB data in multiple slices.
* => Slow in Internet Explorer on new Blob(...)
*/
function getBlobDataSliced() {
var slice,
byteArrays = [];
for (var offset = 0; offset < byteCharacters.length; offset += sliceSize) {
slice = byteCharacters.slice(offset, offset + sliceSize);
byteNumbers = new Array(slice.length);
for (var i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
byteArray = new Uint8Array(byteNumbers);
// Add slice
byteArrays.push(byteArray);
}
return byteArrays;
}
}

The method with fetch is the best solution, but if anyone needs to use a method without fetch then here it is, as the ones mentioned previously didn't work for me:
function makeblob(dataURL) {
const BASE64_MARKER = ';base64,';
const parts = dataURL.split(BASE64_MARKER);
const contentType = parts[0].split(':')[1];
const raw = window.atob(parts[1]);
const rawLength = raw.length;
const uInt8Array = new Uint8Array(rawLength);
for (let i = 0; i < rawLength; ++i) {
uInt8Array[i] = raw.charCodeAt(i);
}
return new Blob([uInt8Array], { type: contentType });
}

In browser just
Uint8Array.from(atob(YOUR_BASE64_DATA), (c) => c.charCodeAt(0))
compare with fetch
!(async () => {
const start = performance.now();
let i = 0;
while (i++ < 1e3) {
const dataUrl =
"data:application/octet-stream;base64,H4sIAAAAAAAAA0vOzyvOz0nVy8lP10jISM3JyVdIr8osUFCpdkksSdXLyy/X0KxN0ORKHlU3qm5U3ai6UXWj6kauOgBVt1KRLwcAAA==";
body = await (await fetch(dataUrl)).blob();
}
console.log(performance.now() - start); // 508.19999999925494ms
})();
!(async () => {
const start = performance.now();
let i = 0;
while (i++ < 1e3) {
const base64Data =
"H4sIAAAAAAAAA0vOzyvOz0nVy8lP10jISM3JyVdIr8osUFCpdkksSdXLyy/X0KxN0ORKHlU3qm5U3ai6UXWj6kauOgBVt1KRLwcAAA==";
body = Uint8Array.from(atob(base64Data), (c) => c.charCodeAt(0));
}
console.log(performance.now() - start); // 7.899999998509884ms
})();
Depends on your data size, choose performance one.

Two different variations
function base64ToBlob(base64, contentType='image/png', chunkLength=512) {
const byteCharsArray = Array.from(atob(base64.substr(base64.indexOf(',') + 1)));
const chunksIterator = new Array(Math.ceil(byteCharsArray.length / chunkLength));
const bytesArrays = [];
for (let c = 0; c < chunksIterator.length; c++) {
bytesArrays.push(new Uint8Array(byteCharsArray.slice(c * chunkLength, chunkLength * (c + 1)).map(s => s.charCodeAt(0))));
}
const blob = new Blob(bytesArrays, {type: contentType});
return blob;
}
/* Not sure how it performs with big images */
async function base64ToBlobLight(base64) { return await fetch(base64).then(res => res.blob()); }
/* Test */
const base64Data = 'data:image/png;base64,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';
const blob = base64ToBlob(base64Data);
const blobUrl = URL.createObjectURL(blob);
const img = document.createElement('img');
img.src = blobUrl;
document.body.appendChild(img);
/**********************/
/* Test */
(async () => {
const blob = await base64ToBlobLight(base64Data);
const blobUrl = URL.createObjectURL(blob);
const img = document.createElement('img');
img.src = blobUrl;
document.body.appendChild(img);
})();

This would prove to be much short solution.
const byteArray = new Buffer(base64String.replace(/^[\w\d;:\/]+base64\,/g, ''), 'base64');
base64String is the string containing the base 64 string.
byteArray is the array you need.
The regex replacement is optional and is just there to deal with prefix as in the case of dataurl string.

ie11 Downloading Base64 documents

I have tried pretty much everything at this point and I cannot get anything to work in ie.
I need ie to download base64 documents from an attachment panel. I have no access to the server side code or database. The images cannot be stored in a folder to be pulled up, they need to be presented this way.
I have tried using a plain link and sticking the base64 sting in there and it just opens up a new blank window.
<a target="_blank" download class="btn btn-primary downloadAttachment" href="' + blobUrl + '" >Download</a>
I have tried turning the url into a blob and opening the blob and that resulted in the browser not doing anything.
function base64toBlob(base64Data, contentType) {
contentType = contentType || '';
var sliceSize = 1024;
var byteCharacters = base64Data;
var bytesLength = byteCharacters.length;
var slicesCount = Math.ceil(bytesLength / sliceSize);
var byteArrays = new Array(slicesCount);
for (var sliceIndex = 0; sliceIndex < slicesCount; ++sliceIndex) {
var begin = sliceIndex * sliceSize;
var end = Math.min(begin + sliceSize, bytesLength);
var bytes = new Array(end - begin);
for (var offset = begin, i = 0 ; offset < end; ++i, ++offset) {
bytes[i] = byteCharacters[offset].charCodeAt(0);
}
byteArrays[sliceIndex] = new Uint8Array(bytes);
}
return new Blob(byteArrays, { type: contentType });
}
I am completely and totally stuck. I have tried everything from google and on here.
My two latest attempts here
https://jsfiddle.net/pqhdce2L/
http://jsfiddle.net/VB59f/464/

Some time ago I've coined this function to make ("offer/initialize") a download of an xlsx or csv content accepting both a Blob or a base64 string:
// Initializes a file download of a provided content
//
// Not usable outside browser (depends on window & document)
//
// #param {Blob|base64} cont File content as blob or base64 string
// #param {string} ftype File type (extension)
// #param {string} [fname='export.' + ftype] File name
// #param {string} [mime='application/zip'] File mime type
// #returns {void}
function makeFileDownload(cont, ftype, fname, mime) {
if (!fname) fname = 'export.' + ftype;
if (!mime) mime = ftype === 'csv' ? 'text/csv' : 'application/zip'; // or 'application/vnd.ms-excel'
if (Object.prototype.toString.call(cont) === '[object Blob]'
&& window.navigator && window.navigator.msSaveBlob) {
window.navigator.msSaveBlob(cont, fname);
}
else {
var downloadLink = document.createElement('a');
downloadLink.download = fname;
downloadLink.href = typeof cont === 'string'
? 'data:' + mime + ';base64,' + cont
: window.URL.createObjectURL(cont);
downloadLink.onclick = function(e) { document.body.removeChild(e.target); };
downloadLink.style.display = 'none';
document.body.appendChild(downloadLink);
downloadLink.click();
}
};
This should be able to accept both Blob and base64 string - you should get the idea how it's being done for either a Blob and a base64 string from the if/else block.
If passing it base64 string is problematic just convert it to a Blob first (as suggested for example in this SO question, this answer is specifically aimed at IE11). Adjust the mime defaults according to your expected usage.
I suppose you already have the content (Blob/base64), keep your original link (which I suppose is to be clicked by an user) a plain link or rather a button (i.e. without the download/href attributes), attach it a click event handler where you'll call the function and it should initialize the download for you:
document.querySelector('#originalLink').addEventListener('click', function () {
makeFileDownload(content, extension, filename, mimetype);
});

If you are trying to generate blob URL in IE, it will not work.
We have to download the file to local by using below code:
function printPdf(id) {
$.ajax({
url: 'url',
type: 'POST',
data: { 'ID': id },
success: function (result) {
var blob = pdfBlobConvesion(result.PdfUrl, 'application/pdf');
var isIE = /*#cc_on!#*/false || !!document.documentMode;
// Edge 20+
var isEdge = !isIE && !!window.StyleMedia;
if (isIE || isEdge) {
window.navigator.msSaveOrOpenBlob(blob, "ProviderOfficePDF.pdf");
}
else {
var blobUrl = URL.createObjectURL(blob);
window.open(blobUrl, "_blank");
}
}
});
}
function pdfBlobConvesion(b64Data, contentType) {
contentType = contentType || '';
var sliceSize = 512;
b64Data = b64Data.replace(/^[^,]+,/, '');
b64Data = b64Data.replace(/\s/g, '');
var byteCharacters = window.atob(b64Data);
var byteArrays = [];
for ( var offset = 0; offset < byteCharacters.length; offset = offset + sliceSize ) {
var slice = byteCharacters.slice(offset, offset + sliceSize);
var byteNumbers = new Array(slice.length);
for (var i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
var byteArray = new Uint8Array(byteNumbers);
byteArrays.push(byteArray);
}
var blob = new Blob(byteArrays, { type: contentType });
return blob;
}

IE, in classic fashion, requires you to use a proprietary method for "saving" a blob.
msSaveBlob or msSaveOrOpenBlob is what you're looking for.
Instead of adding it as the href, add an onclick handler to your a tag and call navigator.msSaveBlob(blob, "Sample Name");
Additionally if you need to support other browsers you'll need some other code to support those browsers.
For example:
var content = new Blob(["Hello world!"], { type: 'text/plain' });
var btn = document.getElementById('btn');
if (navigator.msSaveBlob) {
btn.onclick = download;
} else {
btn.href = URL.createObjectURL(content);
btn.download = true;
}
function download() {
if (navigator.msSaveBlob) {
navigator.msSaveBlob(content, "sample.txt");
}
}
<a id="btn" href="#">Download the text!</a>

var data = item;
var fileName = name;
if (window.navigator && window.navigator.msSaveOrOpenBlob) { // IE
workaround
var byteCharacters = atob(data);
var byteNumbers = new Array(byteCharacters.length);
for (var i = 0; i < byteCharacters.length; i++) {
byteNumbers[i] = byteCharacters.charCodeAt(i);
}
var byteArray = new Uint8Array(byteNumbers);
var blob = new Blob([byteArray], {type: 'application/octet-stream'});
window.navigator.msSaveOrOpenBlob(blob, fileName);
}
else if( agent.indexOf('firefox') > -1)
{
console.log(extention,'item111')
var byteCharacters = atob(data);
var byteNumbers = new Array(byteCharacters.length);
for (var i = 0; i < byteCharacters.length; i++) {
byteNumbers[i] = byteCharacters.charCodeAt(i);
}
var byteArray = new Uint8Array(byteNumbers);
//var FileSaver = require('file-saver');
var blob = new Blob([byteArray], {type: "application/octet-stream"});
saveAs(blob, fileName);
}
else{
this.fileDownload='data:application/octet-stream;base64,'+item;
var link = document.createElement("a");
const fileName=name;
link.href = this.fileDownload;
link.download=fileName;
link.click();
}
}

How shall I read out data from a binary Excel from node.js REST API file and display it in HTML using Angularjs

I'm getting binary excel(.xls) data from node.js REST API, now I need to consume this service in Angular controller and convert this binary excel(.xls) file and preview the Excel in my project directly without downloading.
My code is
$scope.exportToExcel = function () {
function b64toBlob(b64Data, contentType, sliceSize) {
contentType = contentType || '';
sliceSize = sliceSize || 512;
var byteCharacters = atob(b64Data);
var byteArrays = [];
for (var offset = 0; offset < byteCharacters.length; offset += sliceSize) {
var slice = byteCharacters.slice(offset, offset + sliceSize);
var byteNumbers = new Array(slice.length);
for (var i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
var byteArray = new Uint8Array(byteNumbers);
byteArrays.push(byteArray);
}
var blob = new Blob(byteArrays, { type: contentType });
return blob;
}
var contentType = 'binary/octet-stream';
var b64Data = data;
var convert = b64toBlob(b64Data, contentType);
// var blob = URL.createObjectURL(convert);
console.log("DOWNLOAD: " + URL.createObjectURL(convert))
saveAs(convert, "Report.xls");
}
On Click action this code runs and download the binary data as excel file, but instead of downloading I need to directly display it in browser, I'm using Angularjs
Please guide me in this. Thanks

Have <audio> element play through earpiece

In a webpage environment, is there a way to force the audio to play through the earpiece instead of through the loudspeaker as it does by default? Here is my code that plays the base64 encoded blob to the loudspeaker:
<p><audio id="audio" controls></audio></p>
<script>
// me saying "test"
var message = "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";
function b64toBlob(b64Data, contentType, sliceSize) {
contentType = contentType || '';
sliceSize = sliceSize || 512;
var byteCharacters = atob(b64Data);
var byteArrays = [];
for (var offset = 0; offset < byteCharacters.length; offset += sliceSize) {
var slice = byteCharacters.slice(offset, offset + sliceSize);
var byteNumbers = new Array(slice.length);
for (var i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
var byteArray = new Uint8Array(byteNumbers);
byteArrays.push(byteArray);
}
var blob = new Blob(byteArrays, {type: contentType});
return blob;
}
var blob = b64toBlob(message, "video/webm");
var audio = document.getElementById('audio');
audio.src = URL.createObjectURL(blob);
audio.play();
</script>

You should be able to use HTMLMediaElement.setSinkId() to achieve this. Please note that that function is part of an experimental API. Only a few browsers (Chrome 49 and Opera 36) support it at the moment.
async function setupAudioOutput(audio) {
const devices = await navigator.mediaDevices.enumerateDevices();
const audioDevices = devices.filter(device => device.kind === 'audiooutput');
await audio.setSinkId(audioDevices[0].deviceId);
}
Call this function after your <audio> element was created and pass it as an argument.

Convert Data URI to File then append to FormData

I've been trying to re-implement an HTML5 image uploader like the one on the Mozilla Hacks site, but that works with WebKit browsers. Part of the task is to extract an image file from the canvas object and append it to a FormData object for upload.
The issue is that while canvas has the toDataURL function to return a representation of the image file, the FormData object only accepts File or Blob objects from the File API.
The Mozilla solution used the following Firefox-only function on canvas:
var file = canvas.mozGetAsFile("foo.png");
...which isn't available on WebKit browsers. The best solution I could think of is to find some way to convert a Data URI into a File object, which I thought might be part of the File API, but I can't for the life of me find something to do that.
Is it possible? If not, any alternatives?

After playing around with a few things, I managed to figure this out myself.
First of all, this will convert a dataURI to a Blob:
function dataURItoBlob(dataURI) {
// convert base64/URLEncoded data component to raw binary data held in a string
var byteString;
if (dataURI.split(',')[0].indexOf('base64') >= 0)
byteString = atob(dataURI.split(',')[1]);
else
byteString = unescape(dataURI.split(',')[1]);
// separate out the mime component
var mimeString = dataURI.split(',')[0].split(':')[1].split(';')[0];
// write the bytes of the string to a typed array
var ia = new Uint8Array(byteString.length);
for (var i = 0; i < byteString.length; i++) {
ia[i] = byteString.charCodeAt(i);
}
return new Blob([ia], {type:mimeString});
}
From there, appending the data to a form such that it will be uploaded as a file is easy:
var dataURL = canvas.toDataURL('image/jpeg', 0.5);
var blob = dataURItoBlob(dataURL);
var fd = new FormData(document.forms[0]);
fd.append("canvasImage", blob);

BlobBuilder and ArrayBuffer are now deprecated, here is the top comment's code updated with Blob constructor:
function dataURItoBlob(dataURI) {
var binary = atob(dataURI.split(',')[1]);
var array = [];
for(var i = 0; i < binary.length; i++) {
array.push(binary.charCodeAt(i));
}
return new Blob([new Uint8Array(array)], {type: 'image/jpeg'});
}

This one works in iOS and Safari.
You need to use Stoive's ArrayBuffer solution but you can't use BlobBuilder, as vava720 indicates, so here's the mashup of both.
function dataURItoBlob(dataURI) {
var byteString = atob(dataURI.split(',')[1]);
var ab = new ArrayBuffer(byteString.length);
var ia = new Uint8Array(ab);
for (var i = 0; i < byteString.length; i++) {
ia[i] = byteString.charCodeAt(i);
}
return new Blob([ab], { type: 'image/jpeg' });
}

Firefox has canvas.toBlob() and canvas.mozGetAsFile() methods.
But other browsers do not.
We can get dataurl from canvas and then convert dataurl to blob object.
Here is my dataURLtoBlob() function. It's very short.
function dataURLtoBlob(dataurl) {
var arr = dataurl.split(','), mime = arr[0].match(/:(.*?);/)[1],
bstr = atob(arr[1]), n = bstr.length, u8arr = new Uint8Array(n);
while(n--){
u8arr[n] = bstr.charCodeAt(n);
}
return new Blob([u8arr], {type:mime});
}
Use this function with FormData to handle your canvas or dataurl.
For example:
var dataurl = canvas.toDataURL('image/jpeg',0.8);
var blob = dataURLtoBlob(dataurl);
var fd = new FormData();
fd.append("myFile", blob, "thumb.jpg");
Also, you can create a HTMLCanvasElement.prototype.toBlob method for non gecko engine browser.
if(!HTMLCanvasElement.prototype.toBlob){
HTMLCanvasElement.prototype.toBlob = function(callback, type, encoderOptions){
var dataurl = this.toDataURL(type, encoderOptions);
var bstr = atob(dataurl.split(',')[1]), n = bstr.length, u8arr = new Uint8Array(n);
while(n--){
u8arr[n] = bstr.charCodeAt(n);
}
var blob = new Blob([u8arr], {type: type});
callback.call(this, blob);
};
}
Now canvas.toBlob() works for all modern browsers not only Firefox.
For example:
canvas.toBlob(
function(blob){
var fd = new FormData();
fd.append("myFile", blob, "thumb.jpg");
//continue do something...
},
'image/jpeg',
0.8
);

My preferred way is canvas.toBlob()
But anyhow here is yet another way to convert base64 to a blob using fetch ^^,
var url = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg=="
fetch(url)
.then(res => res.blob())
.then(blob => {
var fd = new FormData()
fd.append('image', blob, 'filename')
console.log(blob)
// Upload
// fetch('upload', {method: 'POST', body: fd})
})

Thanks to #Stoive and #vava720 I combined the two in this way, avoiding to use the deprecated BlobBuilder and ArrayBuffer
function dataURItoBlob(dataURI) {
'use strict'
var byteString,
mimestring
if(dataURI.split(',')[0].indexOf('base64') !== -1 ) {
byteString = atob(dataURI.split(',')[1])
} else {
byteString = decodeURI(dataURI.split(',')[1])
}
mimestring = dataURI.split(',')[0].split(':')[1].split(';')[0]
var content = new Array();
for (var i = 0; i < byteString.length; i++) {
content[i] = byteString.charCodeAt(i)
}
return new Blob([new Uint8Array(content)], {type: mimestring});
}

The evolving standard looks to be canvas.toBlob() not canvas.getAsFile() as Mozilla hazarded to guess.
I don't see any browser yet supporting it :(
Thanks for this great thread!
Also, anyone trying the accepted answer should be careful with BlobBuilder as I'm finding support to be limited (and namespaced):
var bb;
try {
bb = new BlobBuilder();
} catch(e) {
try {
bb = new WebKitBlobBuilder();
} catch(e) {
bb = new MozBlobBuilder();
}
}
Were you using another library's polyfill for BlobBuilder?

var BlobBuilder = (window.MozBlobBuilder || window.WebKitBlobBuilder || window.BlobBuilder);
can be used without the try catch.
Thankx to check_ca. Great work.

The original answer by Stoive is easily fixable by changing the last line to accommodate Blob:
function dataURItoBlob (dataURI) {
// convert base64 to raw binary data held in a string
// doesn't handle URLEncoded DataURIs
var byteString;
if (dataURI.split(',')[0].indexOf('base64') >= 0)
byteString = atob(dataURI.split(',')[1]);
else
byteString = unescape(dataURI.split(',')[1]);
// separate out the mime component
var mimeString = dataURI.split(',')[0].split(':')[1].split(';')[0];
// write the bytes of the string to an ArrayBuffer
var ab = new ArrayBuffer(byteString.length);
var ia = new Uint8Array(ab);
for (var i = 0; i < byteString.length; i++) {
ia[i] = byteString.charCodeAt(i);
}
// write the ArrayBuffer to a blob, and you're done
return new Blob([ab],{type: mimeString});
}

Here is an ES6 version of Stoive's answer:
export class ImageDataConverter {
constructor(dataURI) {
this.dataURI = dataURI;
}
getByteString() {
let byteString;
if (this.dataURI.split(',')[0].indexOf('base64') >= 0) {
byteString = atob(this.dataURI.split(',')[1]);
} else {
byteString = decodeURI(this.dataURI.split(',')[1]);
}
return byteString;
}
getMimeString() {
return this.dataURI.split(',')[0].split(':')[1].split(';')[0];
}
convertToTypedArray() {
let byteString = this.getByteString();
let ia = new Uint8Array(byteString.length);
for (let i = 0; i < byteString.length; i++) {
ia[i] = byteString.charCodeAt(i);
}
return ia;
}
dataURItoBlob() {
let mimeString = this.getMimeString();
let intArray = this.convertToTypedArray();
return new Blob([intArray], {type: mimeString});
}
}
Usage:
const dataURL = canvas.toDataURL('image/jpeg', 0.5);
const blob = new ImageDataConverter(dataURL).dataURItoBlob();
let fd = new FormData(document.forms[0]);
fd.append("canvasImage", blob);

Thanks! #steovi for this solution.
I have added support to ES6 version and changed from unescape to dataURI(unescape is deprecated).
converterDataURItoBlob(dataURI) {
let byteString;
let mimeString;
let ia;
if (dataURI.split(',')[0].indexOf('base64') >= 0) {
byteString = atob(dataURI.split(',')[1]);
} else {
byteString = encodeURI(dataURI.split(',')[1]);
}
// separate out the mime component
mimeString = dataURI.split(',')[0].split(':')[1].split(';')[0];
// write the bytes of the string to a typed array
ia = new Uint8Array(byteString.length);
for (var i = 0; i < byteString.length; i++) {
ia[i] = byteString.charCodeAt(i);
}
return new Blob([ia], {type:mimeString});
}

make it simple :D
function dataURItoBlob(dataURI,mime) {
// convert base64 to raw binary data held in a string
// doesn't handle URLEncoded DataURIs
var byteString = window.atob(dataURI);
// separate out the mime component
// write the bytes of the string to an ArrayBuffer
//var ab = new ArrayBuffer(byteString.length);
var ia = new Uint8Array(byteString.length);
for (var i = 0; i < byteString.length; i++) {
ia[i] = byteString.charCodeAt(i);
}
// write the ArrayBuffer to a blob, and you're done
var blob = new Blob([ia], { type: mime });
return blob;
}

toDataURL gives you a string and you can put that string to a hidden input.

I had exactly the same problem as Ravinder Payal, and I've found the answer. Try this:
var dataURL = canvas.toDataURL("image/jpeg");
var name = "image.jpg";
var parseFile = new Parse.File(name, {base64: dataURL.substring(23)});