Base64 encoding and decoding in client-side Javascript

Question

Are there any methods in JavaScript that could be used to encode and decode a string using base64 encoding?

Answer 1

Internet Explorer 10+

// Define the string
var string = 'Hello World!';

// Encode the String
var encodedString = btoa(string);
console.log(encodedString); // Outputs: "SGVsbG8gV29ybGQh"

// Decode the String
var decodedString = atob(encodedString);
console.log(decodedString); // Outputs: "Hello World!"

---

Cross-Browser

Re-written and modularized UTF-8 and Base64 Javascript Encoding and Decoding Libraries / Modules for AMD, CommonJS, Nodejs and Browsers. Cross-browser compatible.

---

with Node.js

Here is how you encode normal text to base64 in Node.js:

//Buffer() requires a number, array or string as the first parameter, and an optional encoding type as the second parameter. 
// Default is utf8, possible encoding types are ascii, utf8, ucs2, base64, binary, and hex
var b = new Buffer('JavaScript');
// If we don't use toString(), JavaScript assumes we want to convert the object to utf8.
// We can make it convert to other formats by passing the encoding type to toString().
var s = b.toString('base64');

And here is how you decode base64 encoded strings:

var b = new Buffer('SmF2YVNjcmlwdA==', 'base64')
var s = b.toString();

---

with Dojo.js

To encode an array of bytes using dojox.encoding.base64:

var str = dojox.encoding.base64.encode(myByteArray);

To decode a base64-encoded string:

var bytes = dojox.encoding.base64.decode(str)

---

bower install angular-base64

<script src="bower_components/angular-base64/angular-base64.js"></script>

angular
    .module('myApp', ['base64'])
    .controller('myController', [

    '$base64', '$scope', 
    function($base64, $scope) {
    
        $scope.encoded = $base64.encode('a string');
        $scope.decoded = $base64.decode('YSBzdHJpbmc=');
}]);

---

But How?

If you would like to learn more about how base64 is encoded in general, and in JavaScript in-particular, I would recommend this article: Computer science in JavaScript: Base64 encoding

Answer 2

I'd rather use the bas64 encode/decode methods from CryptoJS, the most popular library for standard and secure cryptographic algorithms implemented in JavaScript using best practices and patterns.

Answer 3

Short and fast Base64 JavaScript Decode Function without Failsafe:

function decode_base64 (s)
{
    var e = {}, i, k, v = [], r = '', w = String.fromCharCode;
    var n = [[65, 91], [97, 123], [48, 58], [43, 44], [47, 48]];

    for (z in n)
    {
        for (i = n[z][0]; i < n[z][1]; i++)
        {
            v.push(w(i));
        }
    }
    for (i = 0; i < 64; i++)
    {
        e[v[i]] = i;
    }

    for (i = 0; i < s.length; i+=72)
    {
        var b = 0, c, x, l = 0, o = s.substring(i, i+72);
        for (x = 0; x < o.length; x++)
        {
            c = e[o.charAt(x)];
            b = (b << 6) + c;
            l += 6;
            while (l >= 8)
            {
                r += w((b >>> (l -= 8)) % 256);
            }
         }
    }
    return r;
}

Answer 4

For what it's worth, I got inspired by the other answers and wrote a small utility which calls the platform specific APIs to be used universally from either Node.js or a browser:

/**
 * Encode a string of text as base64
 *
 * @param data The string of text.
 * @returns The base64 encoded string.
 */
function encodeBase64(data: string) {
    if (typeof btoa === "function") {
        return btoa(data);
    } else if (typeof Buffer === "function") {
        return Buffer.from(data, "utf-8").toString("base64");
    } else {
        throw new Error("Failed to determine the platform specific encoder");
    }
}

/**
 * Decode a string of base64 as text
 *
 * @param data The string of base64 encoded text
 * @returns The decoded text.
 */
function decodeBase64(data: string) {
    if (typeof atob === "function") {
        return atob(data);
    } else if (typeof Buffer === "function") {
        return Buffer.from(data, "base64").toString("utf-8");
    } else {
        throw new Error("Failed to determine the platform specific decoder");
    }
}

Answer 5

function b64_to_utf8( str ) {
  return decodeURIComponent(escape(window.atob( str )));
}

https://developer.mozilla.org/en-US/docs/Web/API/WindowBase64/Base64_encoding_and_decoding#The_.22Unicode_Problem.22

Answer 6

I have tried the Javascript routines at phpjs.org and they have worked well.

I first tried the routines suggested in the chosen answer by Ranhiru Cooray - http://ntt.cc/2008/01/19/base64-encoder-decoder-with-javascript.html

I found that they did not work in all circumstances. I wrote up a test case where these routines fail and posted them to GitHub at:

https://github.com/scottcarter/base64_javascript_test_data.git

I also posted a comment to the blog post at ntt.cc to alert the author (awaiting moderation - the article is old so not sure if comment will get posted).