[javascript] Saving binary data as file using JavaScript from a browser

I am working on a business application using angularJS. One of my service method returning me a byte[] (inclding PDF file content) now i need to download this file as PDF to client machine using JavaScript.

How is that possible using HTML5 Apis or any JavaScript API?

I have used window.atob(base64String)

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

but getting this following error Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded.

To do this task download.js library can be used. Here is an example from library docs:

download("data:image/gif;base64,R0lGODlhRgAVAIcAAOfn5+/v7/f39////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////yH5BAAAAP8ALAAAAABGABUAAAj/AAEIHAgggMGDCAkSRMgwgEKBDRM+LBjRoEKDAjJq1GhxIMaNGzt6DAAypMORJTmeLKhxgMuXKiGSzPgSZsaVMwXUdBmTYsudKjHuBCoAIc2hMBnqRMqz6MGjTJ0KZcrz5EyqA276xJrVKlSkWqdGLQpxKVWyW8+iJcl1LVu1XttafTs2Lla3ZqNavAo37dm9X4eGFQtWKt+6T+8aDkxUqWKjeQUvfvw0MtHJcCtTJiwZsmLMiD9uplvY82jLNW9qzsy58WrWpDu/Lp0YNmPXrVMvRm3T6GneSX3bBt5VeOjDemfLFv1XOW7kncvKdZi7t/S7e2M3LkscLcvH3LF7HwSuVeZtjuPPe2d+GefPrD1RpnS6MGdJkebn4/+oMSAAOw==", "dlDataUrlBin.gif", "image/gif");

Try

let bytes = [65,108,105,99,101,39,115,32,65,100,118,101,110,116,117,114,101];_x000D_
_x000D_
let base64data = btoa(String.fromCharCode.apply(null, bytes));_x000D_
_x000D_
let a = document.createElement('a');_x000D_
a.href = 'data:;base64,' + base64data;_x000D_
a.download = 'binFile.txt'; _x000D_
a.click();

I convert here binary data to base64 (for bigger data conversion use this) - during downloading browser decode it automatically and save raw data in file. 2020.06.14 I upgrade Chrome to 83.0 and above SO snippet stop working (probably due to sandbox security restrictions) - but JSFiddle version works - here

Use FileSaver.js. It supports Chrome, Edge, Firefox, and IE 10+ (and probably IE < 10 with a few "polyfills" - see Note 4). FileSaver.js implements the saveAs() FileSaver interface in browsers that do not natively support it:
     https://github.com/eligrey/FileSaver.js

Minified version is really small at < 2.5KB, gzipped < 1.2KB.

Usage:

/* TODO: replace the blob content with your byte[] */
var blob = new Blob([yourBinaryDataAsAnArrayOrAsAString], {type: "application/octet-stream"});
var fileName = "myFileName.myExtension";
saveAs(blob, fileName);

You might need Blob.js in some browsers (see Note 3). Blob.js implements the W3C Blob interface in browsers that do not natively support it. It is a cross-browser implementation:
     https://github.com/eligrey/Blob.js

Consider StreamSaver.js if you have files larger than blob's size limitations.

Complete example:

/* Two options_x000D_
 * 1. Get FileSaver.js from here_x000D_
 *     https://github.com/eligrey/FileSaver.js/blob/master/FileSaver.min.js -->_x000D_
 *     <script src="FileSaver.min.js" />_x000D_
 *_x000D_
 * Or_x000D_
 *_x000D_
 * 2. If you want to support only modern browsers like Chrome, Edge, Firefox, etc., _x000D_
 *    then a simple implementation of saveAs function can be:_x000D_
 */_x000D_
function saveAs(blob, fileName) {_x000D_
    var url = window.URL.createObjectURL(blob);_x000D_
_x000D_
    var anchorElem = document.createElement("a");_x000D_
    anchorElem.style = "display: none";_x000D_
    anchorElem.href = url;_x000D_
    anchorElem.download = fileName;_x000D_
_x000D_
    document.body.appendChild(anchorElem);_x000D_
    anchorElem.click();_x000D_
_x000D_
    document.body.removeChild(anchorElem);_x000D_
_x000D_
    // On Edge, revokeObjectURL should be called only after_x000D_
    // a.click() has completed, atleast on EdgeHTML 15.15048_x000D_
    setTimeout(function() {_x000D_
        window.URL.revokeObjectURL(url);_x000D_
    }, 1000);_x000D_
}_x000D_
_x000D_
(function() {_x000D_
    // convert base64 string to byte array_x000D_
    var byteCharacters = atob("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");_x000D_
    var byteNumbers = new Array(byteCharacters.length);_x000D_
    for (var i = 0; i < byteCharacters.length; i++) {_x000D_
        byteNumbers[i] = byteCharacters.charCodeAt(i);_x000D_
    }_x000D_
    var byteArray = new Uint8Array(byteNumbers);_x000D_
    _x000D_
    // now that we have the byte array, construct the blob from it_x000D_
    var blob1 = new Blob([byteArray], {type: "application/octet-stream"});_x000D_
_x000D_
    var fileName1 = "cool.gif";_x000D_
    saveAs(blob1, fileName1);_x000D_
_x000D_
    // saving text file_x000D_
    var blob2 = new Blob(["cool"], {type: "text/plain"});_x000D_
    var fileName2 = "cool.txt";_x000D_
    saveAs(blob2, fileName2);_x000D_
})();

Tested on Chrome, Edge, Firefox, and IE 11 (use FileSaver.js for supporting IE 11).
You can also save from a canvas element. See https://github.com/eligrey/FileSaver.js#saving-a-canvas.

Demos: https://eligrey.com/demos/FileSaver.js/

Blog post by author of FileSaver.js: http://eligrey.com/blog/post/saving-generated-files-on-the-client-side

Note 1: Browser support: https://github.com/eligrey/FileSaver.js#supported-browsers

Note 2: Failed to execute 'atob' on 'Window'

Note 3: Polyfill for browsers not supporting Blob: https://github.com/eligrey/Blob.js
                See http://caniuse.com/#search=blob

Note 4: IE < 10 support (I've not tested this part):
                https://github.com/eligrey/FileSaver.js#ie--10
                https://github.com/eligrey/FileSaver.js/issues/56#issuecomment-30917476

Downloadify is a Flash-based polyfill for supporting IE6-9: https://github.com/dcneiner/downloadify (I don't recommend Flash-based solutions in general, though.)
Demo using Downloadify and FileSaver.js for supporting IE6-9 also: http://sheetjs.com/demos/table.html

Note 5: Creating a BLOB from a Base64 string in JavaScript

Note 6: FileSaver.js examples: https://github.com/eligrey/FileSaver.js#examples