While Node.js has built-in support for Base64 data, it does not come with the ability to encode / decode data in a stream.

This library contains a streaming Base64 encoder and a streaming Base64 decoder for use with Node.js. These classes are written using the Node.js stream interfaces and are well covered with unit tests.

To install base64-stream

npm install base64-stream

This example encodes an image and pipes it to stdout.

var http = require('http');
var {Base64Encode} = require('base64-stream');

var img = 'http://farm3.staticflickr.com/2433/3973241798_86ddfa642b_o.jpg';
http.get(img, function(res) {
    if (res.statusCode === 200)
        res.pipe(new Base64Encode()).pipe(process.stdout);
});

This example takes in Base64 encoded data on stdin, decodes it, an pipes it to stdout.

var {Base64Decode} = require('base64-stream');
process.stdin.pipe(new Base64Decode()).pipe(process.stdout);

Base64Encode can take an optional object {lineLength: number, prefix: string}
The prefix is useful for prepending for example data:image/png;base64, to make a base64 URL.
This example proxies an image url, and send the base64 string in response.

app.get('/i/*', function(req, res){ // using express for example
	fetch(req.params[0]) // using node-fetch
	.then(r=>r.body.pipe(new Base64Encode({prefix:`data:${r.headers.get('content-type')};base64,`})).pipe(res))
	.catch(console.error);
});

This module currently requires Node 6.0.0 or higher.

To run the unit tests

npm test

MIT